Safeway's agreed bidder WM Morrison, which put a £2.57bn all-share offer on the table last week, has hired Citigate Dewe Rogerson (CDR) after a two-way pitch, on fees believed to be between £250,000 and £1m.
Bell Pottinger Financial chairman Piers Pottinger and MD Jonathan Brill lead Wal-Mart's City PR as the US group considers a hostile bid for Safeway through UK store chain Asda - currently the third biggest supermarket in the UK behind Tesco and Sainsbury.
Industry sources suggest the deal is one of the largest earners for the City PR sector in the last three years, and will account for between 25 and 50 per cent of annual profits for some of the corporate and financial agencies involved.
Brunswick is working with retained client Safeway alongside CDR and Morrison to fight off competition from Sainsbury's and Asda.
Finsbury client Sainsbury's is eyeing a bid in excess of £3 per share for Safeway, valuing the firm at more than £3.15bn, but faces tough questioning from regulators, as does Asda.
Finsbury founder Rupert Younger, who is leading the agency's work on the bid, said: 'Communications is playing a lead role in this.
'Our work involves dealing with the financial media, analysts and institutions and the regulation team have an important part to play sitting alongside the lawyers working with the regulation authorities.'
It is understood the interested bidders will be putting in their submissions to the Office of Fair Trading this week. The OFT is set to make a decision before March on which of the bids will need to be referred to the Competition Commission later in the year.