Herbert Smiths head of M&A, Caroline Goodall, started advising Pilkington earlier this month on preliminary advice relating to an approach the company received from Japanese glass maker rival Nippon Sheet Glass on 31 October. The initial £2bn Nippon offer was rejected last week for being too low.
However, Pilkingtons chairman, Sir Nigel Rudd, is understood to have over-ruled the decision to instruct Herbert Smith and has brought in Slaughters in the firms place.
Rudd, who is also the chairman of Boots and deputy chairman at Barclays, has long-standing links with Slaughters.
Slaughters corporate partner Jeff Triggs is now handling the transaction while Allen & Overy is advising Nippon.
Both Slaughters and Herbert Smith are long-standing advisers to Pilkington, the UK-based glass maker, which has annual revenues of £2.7bn. Herbert Smith has advised the company since the 1980s.
As no formal talks have started between the two companies, Herbert Smiths role is likely to have consisted mainly of advising on discussions regarding valuation and initial tactics.
One corporate partner at a rival magic circle firm commented: "After just one week or so you could easily replace an adviser if you wanted to, but it is very rare to have actually been instructed on a transaction and then be taken off."
The move comes amid the flood of bids for major UK companies in recent weeks, including the London Stock Exchange, P&O and O2, which has sent advisers scrambling both to secure roles and to manage the stream of conflicts.
Slaughters and Herbert Smith declined to comment.