Brookes joined Engine-owned MHP around 18 months ago from BNY Mellon, where he was latterly international head of marketing and corporate affairs.
In a statement, MHP said: "Jamie Brookes joined us in 2014 and helped to develop our strategy for financial services clients with his considerable industry experience. He has now decided that his future lies outside of our firm. We wish him all the very best for the future."
MHP did not comment on whether it had lined up Brookes’ successor.
His departure precedes CEO Gavin Devine’s move to Porta Communications in July, where he will become chief operating officer. Debbie Klein, Engine’s chief executive of Europe and Asia, said: "We are continuing the CEO recruitment process and we look forward to being able to provide an update in due course."
Other senior staff changes at the agency this year have included Ian Kirby’s promotion to corporate MD.
MHP reported flat UK revenue of £16.5m in 2015, according to PRWeek’s UK Top 150 table published last week. Recent account wins at MHP have included L'Oréal's UK corporate comms account and The European Federation of Pharmaceutical Industries and Associations.