Grant joined the agency as chairman of public affairs in 1999.
He is returning to the RSPCA, where he was director of comms and campaigns between 1988 and 1991. A statement from B-M said that he has had a ‘lifelong commitment to animal welfare’.
Grant said: ‘I have thoroughly enjoyed my time at Burson-Marsteller but the role of RSPCA chief executive is the one opportunity I could not turn down. I leave at a time when B-M is very much on the up, with the most talented team of staff I have seen in my time here.’
Grant has also worked as director of global corporate and public affairs at The Body Shop and director of public affairs at the Association of Unit Trusts and Investment Funds.
Burson-Marsteller UK CEO Matt Carter said: ‘Over the years Gavin has made a fantastic contribution to Burson-Marsteller’s success. He has been a wise counsellor to both clients and staff alike.
‘I am delighted for Gavin that he can now pursue, in a professional capacity, one of the issues that he has always been so passionate about.’