The firm, headquartered in the UK, is understood to be holding a pitch process for a UK-wide retainer brief after parting with Mercieca.
The successful agency's work will focus on liaising with trade contacts within pub and supermarket publications. The brief is thought to include an element of advertising.
The search for an agency is being led by Rebecca Perry, senior corporate relations manager, corporate and trade media, and Roz Nash, senior category development manager.
A spokeswoman from Diageo said: ‘After eight years of working together, Diageo GB and Mercieca are parting company by mutual consent. Working together on Trade communications we have delivered numerous successful campaigns but have resolved to explore alternative partners.’
The news comes after Diageo comms chief Stephen Doherty was poached by Barclays Bank to take on a newly created role of MD, head of corporate comms. He started the new role on 2 July.
Earlier this year, Diageo pitched its £1m Smirnoff account after which it retained incumbent Splendid Communications. Splendid pitched against GolinHarris, Mischief and 3 Monkeys.