The news follows the group's two year 'revitalisation' project, and a series of votes at its annual general meeting last month.
Tim managed the group for three and a half years after previous incumbent Mike Benner left to take charge of the Society of Independent Brewers (SIBA). He was previously from a charity background, and had been chief executive of the East Anglian Ambulance.
Votes to incorporate a number of new issues into the campaign narrowly lost during the AGM, including support for "all pub-goers and beer, cider and perry drinkers", craft keg beer, and redefining pubs to include tap rooms and cafes serving beer.
But as Inapub editor Robyn Black recently pointed out, the motion to modernise and expand lost by only 3 per cent – and unusually the AGM doesn't require a straight 50 per cent vote, instead seeking a 75 per cent mandate.
Tim said: "I am very grateful for having had the opportunity to be part of CAMRA which is a truly remarkable organisation.
"The past 42 months have seen the campaign maintain its effectiveness in campaigning and lobbying for real ale, cider and perry to be available in every community across the UK; and for those communities to continue to be served by pubs, which provide wide range of benefits for individuals and society as a whole.
"I am grateful for the friendship and support that I have enjoyed from people across the sector, and look forward to keeping in touch with friends within and outside CAMRA."
The group's national chairman, Jackie Parker, said Tim has made a "considerable" impact during his tenure.
"The past three years have seen the campaign engaged in a major strategic review of its purpose and positioning within the sector, and Tim has provided advice and support to the volunteer leadership throughout that process."