Mr Sinclair, best known for creating the pregnant man campaign for the Health Education Council, will also continue as Saatchi's worldwide creative supremo. The move is part of a management shake-up aimed at turning round the troubled Saatchi & Saatchi Advertising network in North America.
Mr Sinclair succeeds Bill Muirhead, who was appointed chief executive of the US network last week, following the forced resignation Bob Kennedy earlier this year with a pounds 4m pay-off. David Kershaw, managing director of Saatchi's flagship London agency, has been prompted to the head of UK operations.
Mr Muirhead's tough brief is to reverse the company's dismal performance in the US, where it has lost key clients including Helene Curtis, the cosmetics firm, and Chrysler, the car maker. However, his first task could involve shoring up Saatchi's relationship with Burger King, for which it handles a multi-million dollar advertising campaign aimed specifically at children.
Reports from the US suggest the restaurant chain has put up its Kids Club account for review alongside the mainstream campaign handled by a rival agency. Industry estimates suggest Burger King spends about dollars 150m on US advertising, of which a significant amount is allocated to the children's campaign.
News of the rumoured review could further unsettle the company's position in the US where it has already lost market share.