His departure follows the appointment of the former United London chairman, Steve Henry, as executive creative director in May last year.
Henry joined above McTear and his fellow joint creative director, Danny Brooke-Taylor, who had run the creative department after Trevor Beattie left to found Beattie McGuinness Bungay in May 2005.
McTear's move could be unsettling for the agency's Sony PlayStation account, on which he has worked for the past four years. He was involved in many of TBWA\London's most famous ads for PlayStation, including the launch campaign for the PSP and the 2004 Cannes Grand Prix-winning "mountain" spot for PlayStation 2.
A spokesman for TBWA\London confirmed that McTear had tendered his resignation, but declined to comment further. McTear did not return calls.