Carter will continue as a senior counsellor to the agency while pursuing his additional interests.
Amanda Pierce will take over from Carter. Pierce, who currently heads the UK and EMEA corporate and crisis practices, joined Burson-Marsteller from McDonald's in 2008.
Carter was general secretary of the Labour Party from 2004 to 2005. He later joined research-focused agency Penn Schoen & Berland Associates, which like Burson-Marsteller is part of WPP, rising to become EMEA MD.
In 2010 he joined Burson-Marsteller as UK CEO while remaining EMEA chairman of Penn Schoen & Berland.
Carter said: 'I have had a fantastic time working at Burson-Marsteller and will continue to be a supporter and an active friend.'
In Carter’s three-and-a-half years heading Burson-Marsteller UK it won its first Cannes Lions awards and was last year declared the Best Large Agency to Work For by PRWeek.
Of Pierce, Burson-Marsteller's EMEA CEO Jeremy Galbraith said: 'Under her leadership the UK corporate & crisis practice has grown steadily and consolidated its position as the biggest practice in the UK office.'