PRWeek understands that SABMiller and Brunswick are to cut ties within weeks, with well-placed sources suggesting Brunswick has resigned its account.
The City's biggest PR firm is widely listed as SABMiller's financial PR agency, but it is thought that the company's financial and investor relations work was taken in-house over recent years and Brunswick's role morphed into comms around alcohol policy.
It is this alcohol policy outreach work that is understood to be up for grabs once the relationship with Brunswick ends, with SABMiller preparing a formal pitch process.
Both Brunswick and SABMiller's head of media relations Nigel Fairbrass declined to comment on the story.
Media reports suggest that SABMiller is currently putting together a further bid for Australian alcohol producer Foster's Group after its June bid was rebuffed.
SABMiller handed the task of handling financial comms on the bid to the Australian arm of Brunswick's rival FD.
Similarly, Brunswick has built relationships with a number of other global alcohol companies, including working on InBev's blockbuster $52bn takeover of fellow brewer Anheuser-Busch in 2008.
Brunswick is also retained to handle financial PR by drinks giant Diageo.
City sources suggested that Brunswick had stepped down from the alcohol policy comms brief over possible conflicts of interest with lucrative clients.
Last year, SAB Miller ended its consumer PR relationship with Shine Communications. Shine said it resigned the account, but SABMiller insisted the agency was dismissed for underachievement.
August 2011 SABMiller readies a multi-billion-dollar syndicated loan to back fresh bid for Fosters.
June 2011 Foster's Group rejects £6.2bn takeover bid from SABMiller as too low.
May 2011 SAB Miller annual profits rise 24 per cent.
July 2010 SAB Miller boss Graham Mackay joins PM David Cameron on a trade visit to India.