Slaughter and May and Milbank Tweed Hadley & McCloy have scooped roles on Singapore ports operator PSA's £3.53bn counterbid for P&O in what promises to be one of the most closely-watched UK acquisitions of the year.

The conditional approach, made yesterday (10 January), tops the £3.3bn agreed offer made by Dubai-based DP World in November for the British container ports and ferries operator – offering 470p per share, compared to 443p.

As reported by Legal Week in November, Slaughters was called in late last year by PSA, which was long expected to launch a counterbid for the ports business.

Slaughter and May head of M&A, Stephen Cooke, is understood to be advising PSA, which is owned by Singapore state investment company Temasek, assisted by corporate partner Gary Eaborn.

Milbank M&A partner Tim Emmerson is acting for PSA adviser Goldman Sachs. The deal is the second high-profile M&A instruction Goldman Sachs has sent Milbank's way in recent weeks, after calling in the US law firm's London arm on Macquarie Bank's ongoing bid for the London Stock Exchange.

Freshfields Bruckhaus Deringer is advising long-standing client P&O with corporate partner Mark Rawlinson leading the team. Linklaters is advising DP World with corporate partners David Cheyne and Jeremy Parr leading.