Immortalised by Kipling, 'if' is a very big word. As the UK general election approaches, it is increasingly punctuating the narrative of lawyers' private conversations as they try to anticipate the potential consequences of 'Brexit' – universal shorthand for Britain's possible exit from the European Union (EU).

Three big 'ifs' must be satisfied as preconditions for this ugly word to take effect: if Britain elects a new Conservative government with an outright majority; if the much-heralded in/out referendum occurs; and if a majority of voters then say 'yes' to EU withdrawal, leading to Britain's unilateral exit.

The first 'if' depends on how the election contest shapes up over the next 100 days. Subject to an unlikely outright Conservative majority on 7 May – predicted by Goldman Sachs, but seen as improbable by most commentators – the second 'if' is likely to happen.

One caveat: you need to accept prime minister David Cameron's repeated 'cast iron' pledges to renegotiate (post-election) the terms of Britain's EU membership – in advance of him putting the result to a referendum by the British people before the end of 2017 (or possibly earlier, according to recent press reports).

The third 'if' is the really big one – despite prominent Conservatives such as London mayor Boris Johnson saying that life outside the clutches of Brussels would not be "cataclysmic", and that "we should be prepared to pull out" of the EU if Cameron's plan to renegotiate Britain's membership fails.

But for innumerable lawyers who have benefited enormously from the single market, this is the nuclear option. A head-to-head europhile v europhobe battle between Triumph and Disaster: unprecedented and, until recently, unthinkable. Unpredictable too, as assorted pollsters have shown 'yes' and 'no' alternately swapping poll positions.

Rather than in its assured status as the undisputed capital of European financial markets, Britain's future in the EU is now located in the tension between these two opposites. "The EU debate is going to become increasingly prised into the general election over the coming months," says James Collis, managing partner at Ashurst.

Predicting the unpredictable – exactly how this might affect law firms and their clients – is invidious for journalists, so we put the relevant questions out to Legal Week readers in a survey. From the results, 33% think British withdrawal over the next five years is 'quite likely' or 'very likely' – pretty much in line with wider polls.

According to Gary Senior (pictured, right), Baker & McKenzie's EMEA chair: "There are those who believe that we're doomed if we stay tied to the eurozone, while others believe it's going to be a disaster for us if we withdraw from the free market with uncertainty as to what sort of trade deal Britain would be able to negotiate outside."

Arguably the world's most geographically diverse law firm, Bakers is used to managing risk in difficult jurisdictions, and Senior is keen to point out that the London office generates only about 10% of the firm's worldwide income.

Brexit: the reaction
So what might Brexit and the referendum leading up to it mean for more UK dependent law firms and for their clients, and what areas of advisory work might receive a boost?

Of itself, the prospect of a referendum does not invoke widespread panic, as reflected in the judgement of one survey respondent: "My gut feel is that the adverse impact on the UK economy in the time leading up to a referendum is probably not going to be that huge, nothing compared to what we've been through with the eurozone crisis."

But on a potential Brexit, the survey provokes much stronger reaction from diverse participants. "Politically and economically, Britain's exit from the EU would be extremely damaging for the country," says one. "It would be a disaster both in regards to clients and law firm employees," argues another. "It would be near impossible for us to attract work from the US and Asia if the UK was not in the EU," laments a third.

"The City and the legal profession need to become more vocal about this issue," one respondent suggests. "We are in denial at the moment, and the Scottish referendum showed how dangerous this can be."

The point is reinforced by another concerned commentator who urges immediate action: "It's crazy. The Law Society and City law firms should be howling from the rooftops to stay in, while at the same time offering help to calm public concerns and reframe the debate."

Although the words 'disaster', 'madness' and 'damaging' proliferate among respondents, there is the occasional dissenting voice: "Those who fear a future free from the EU are, at heart, scared of challenge and innovation and too fond of the cosy status quo."

Perhaps the best response in summarising the consensus reaction comes from Robert Bell, head of the EU competition team at Bryan Cave, who identifies the Brexit dangers. "The majority of Britain's trade is with the EU," he says. "Companies invest in this country on the basis that we are a member of the EU internal market. Any withdrawal will have a significant adverse impact on inward-bound investment into the UK economy. It will also lead to companies relocating their European headquarters from the UK to continental Europe."

Multiple uncertainties
The public response from those managing UK-based commercial law firms is palpably more guarded. At the firm with the largest number of FTSE 100 clients on its books, Slaughter and May, practice partner David Wittmann is understandably circumspect.

"We are at least two years away from having any clarity as to the UK's position in respect of Europe," he explains. "First, we have this year's election and then a possible referendum, at the earliest in 2017. Even if that referendum produces a 'yes' vote, it is currently far from clear as to the terms and conditions of any UK withdrawal from the EU. Of more immediate concern are the ongoing issues in the eurozone, which we continue to keep under review with our clients."

Senior outlines the timetable: "There are a number of phases to this, each with its own uncertainty. At the moment, we don't know whether we're going to have a government that will be committed to a referendum."

Once that is established, he adds: "You then get into the referendum period. There's no doubt that business doesn't like uncertainty and that can cause business to postpone or sometimes cancel investment decisions. We saw some of that around the Scottish referendum, and I'm sure there's going to be a degree of it if we get into a referendum period."

The biggest uncertainty of all, he suggests, is "if we did withdraw from the EU, what that would mean for our economy. Obviously that's going to be a heavily debated issue during a referendum campaign."

Uncertainty for clients in the period leading up to a referendum will inevitably impact directly upon law firms. Collis believes that Ashurst's immediate task will be a watching brief during this period. "As a firm and supporting our clients, we will obviously stay very close to the debate in terms of monitoring it, rather than participating, I suspect," he says. "And as challenges emerge, as inevitably they will when the debate progresses, then we will look to support them as best we can in whatever areas those challenges manifest themselves."

Treading carefully
Charged with managing blue-chip international law firms, Wittmann and Collis stand out, part of only a tiny group of law firm leaders prepared to comment publicly. Among a number of their leading counterparts in UK and international law firms, there is uncharacteristic reluctance to go on the record.

Some choose to stonewall: "That's not a subject I'd wish to speak on," being a typically curt response. Others claim not to pay it much attention: "This is not something we have focused on or have formed a particular strategy for."

More candidly, one managing partner at a top 10 firm reveals their position: "We prefer to keep out of political issues, especially given the upcoming election. We feel it's something we should probably not get too involved in – no doubt we'd probably end up upsetting people, either in the UK or in Europe, no matter what we say."

It is echoed by the chief executive of another big international firm, albeit in more opaque terms: "While we are obviously keeping a close eye on the issue, which is something that we are appraising in respect of our business, we've taken the decision not to speculate on it publicly."

But it is clearly very much on the internal agenda of some big guns, as one global managing partner among their number discloses: "A possible exit by Britain from the EU is something we have a group looking at. However, it is very early days. Therefore, we don't have much in terms of progressed or concluded thinking at this stage."

Glimmer of optimism
Such cautious words, carefully chosen, do little to address the question: what if?
One managing partner prepared to put his head above the parapet and answer it publicly is Simon Beswick (pictured, below) at Osborne Clarke.

"We are strong supporters of the UK remaining in the EU, as we believe it is important for the country's growth over the mid to longer term," he says. "If the UK were to exit the EU then we believe it would do so in a way to preserve a trading relationship with the EU block, which, in the short term, is likely to have little economic impact. For those reasons, we believe that our current strategy of growing our client base in the US and in Asia will serve us well whether the UK remains inside or outside the EU."

Beswick's optimism is based on the premise that, post-exit, Britain would join the European Economic Area, alongside Norway, Iceland and Liechtenstein, or enjoy rights similar to Switzerland in the European Free Trade Association, allowing the single market to remain open.

Collis takes a different approach. "Ashurst, as a firm, doesn't have any position on whether or not the UK should or shouldn't remain in the EU," he comments. "We are political agnostics. But I'm sure that our clients are looking at it and that there are conversations around the business where clients are wondering what may happen." The impact of a possible withdrawal, upon clients and the firm, he adds, is "very hard to assess at this stage".

However, off the record comments suggest that Beswick's view is not universally shared by his opposite numbers in other firms. Unsurprisingly, there are no self-proclaimed Faragists to be found among them. Not pulling his punches, one prominent managing partner confides: "Nigel Farage is bad for business and bad for Britain: he's backward-looking and ill-informed and his incoherent arguments about the EU need to be more effectively challenged."

At present, Wittmann is less concerned. "For Slaughter and May and our European best friends, at the moment we are more interested in our current work for our clients and the effect of issues such as the uncertain situation in Ukraine," he says.

Post-exit workloads
Looking to what advisory work might be anticipated leading up to a referendum, Beswick suggests: "Initially, advice relating to industry-based lobbying for deregulation and, as and when change comes, how that change will affect our clients."

And the impact on Osborne Clarke? "Short term, little. Longer term, we would need to continue to diversify our client base geographically."

Meanwhile, Wittmann is confident that "closer to any referendum, our clients would ask us to help them to work through any potential issues, as they did last year with the Scottish vote, although it is far too early to say what those issues might be".

Beyond the referendum, what additional work might arise post-exit and is there any upside potential? "That will depend upon the pace of change away from EU-originated law and regulation," says Beswick. "At this stage it is too early to say – there are too many contingencies and uncertainties," cautions Wittmann.

Collis adds: "The direct effects on clients are consequential on any legislative changes that would result from a withdrawal. That question can only be answered when we have more clarity around how those negotiations would progress during that period. One thing is pretty clear: uncertainty is bad for business, so to the extent that there is uncertainty, that is clearly going to be a challenge at a commercial level for clients."

Survey respondents are notably more forthcoming about potential growth areas. At one end of the spectrum there is tangible gloom: "I can't think of one that wouldn't benefit." "Initially financial services and, obviously, competition. But, longer term, it would be damaging." "None – the UK would become an unimportant back water with no influence and less business."

Others, however, do highlight growth in everything from banking, finance, capital markets and securitisation to corporate, employment, intellectual property, litigation, insolvency, regulatory and tax. Even M&A is mentioned, albeit only once.

Overall, 14% see withdrawal as being 'quite positive' or 'very positive' for their firm, set against 59% who think it would be 'quite adverse' or 'very adverse'. This is despite 52% anticipating a significant increase in exit-related work being generated.

Jason Phelps, head of EU and competition at Michelmores, explains: "While there might be short-term growth in certain practice areas because of the confusion caused by an EU exit, I have no doubts that it would be a disaster for the UK."

Preparing to act
As multiple Brexit-related issues move into sharper focus in the coming months, lawyers will equally be sharpening their minds to address mounting client concerns. A few 'ifs' satisfied, and an entire strategy rethink may well be needed – by clients and their lawyers.

Senior concludes: "If you're a firm only in the UK, maybe these questions loom larger. Even then, what do you do in terms of expanding or contracting particular practices? If you think this may be about to happen, then you've just got to keep an eye on developments.

"But we need to keep it in perspective. Many things can impact business flows (positively and negatively) – we could have another eurozone crisis over the next two years, which would have a much bigger impact on law firms in the City than the possibility of a referendum. So, being blunt, we live in a much more unstable world and to some extent you've got to roll with the punches."

To forecast with any confidence what may happen in the general election or in a referendum that might follow would be foolish. There are too many 'ifs' in between now and that point.

But pretending that a referendum or Brexit simply won't, or can't, happen is ostrich-like. And as long as it remains a distinct possibility, more lawyers need to be looking for answers to the myriad questions beginning: what if…?

• Click here to view the survey results