Merger talks between UK firm Addleshaw Goddard and US firm Hunton & Williams have stalled following the UK's June vote to leave the European Union (EU).

Partners at the firms told Legal Week that the discussions, which were first reported in May this year but are understood to have begun at the tail end of 2015,  have slowed down in the wake of the EU referendum, in order to assess the impact of Brexit on the UK.

An Addleshaws partner said: "The US deal is still ongoing but it has slowed because the dust hasn't settled on Brexit yet."

The forthcoming US presidential election is also understood to have played a part in the delays.

Nothing has yet been formally put to the partnership at Addleshaws but prior to the Brexit vote, talks between the pair had progressed to a stage where there was a "sufficient degree of conformity that everyone was comfortable with the basics and the feel culturally", according to one Addleshaws partner.

A deal between the pair would create a firm with combined revenue of around £554m and more than 1,300 lawyers.

Hunton has 13 offices across the US, alongside small international outposts in Brussels, Beijing, Tokyo, London and Bangkok, while Addleshaws has three UK offices and international offices in Dubai, Hong Kong, Oman, Qatar and Singapore.

A merger would increase both firms' coverage with relatively little overlap, as the only duplicate office is in London, where Hunton has a six-partner base.

Addleshaws posted revenue of £201.8m for the 2015-16 financial year, up from £192.4m the previous year, while profit per equity partner (PEP) soared by 39% to £682,000, from £491,000.

The firm's results were boosted by fees paid for mandates from previous years, partly connected to the long-running Berezovsky litigation.

In contrast, Hunton's turnover dropped 7% to $528m (£361.6m) in 2015, making it the 62nd largest firm by revenue in the US. Its PEP stood at $950,000 (£650,039), down 5%.

In the past 12 months, Addleshaws has also held merger talks with Scottish firm Maclay Murray & Spens, which were called off earlier this year after the two sides failed to come to an agreement.

Addleshaws declined to comment and Hunton did not respond to requests for comment.

For more see: 'The message has got through that a little UK merger ain't going to cut it' – reaction to the Addleshaws-Hunton talks