Delanoë, Mayor of Paris, to run for Socialist Party Leadership

Outlining his vision for the French left in an exclusive interview with Le Monde, Delanoë said he would put "all his energy" into the campaign, which, if successful, would see him become President Nicolas Sarkozy's chief political rival.

"I will be the first to sign up to a move towards a political project which I would like to lead," he said. "So of course I will accept the foremost task of a party member, if the Socialists will trust me with it."

Delanoë, one of France's first openly gay politicians, was elected mayor in 2001 and has been encouraged in his bid to replace François Hollande as first secretary of the PS (Partie socialiste) by opinion polls which consistently rank him the public's favourite opposition figure. A survey at the weekend indicated 27% of voters would like to see him take over, ahead of Ségolène Royal, last year's failed presidential candidate, on 18%.

Delanoë, who made his name in the capital as an innovator after bringing in the Paris Plage beach project and Vélib bike hire scheme, is viewed by many as a potential force for change. For months he has been preparing the ground for a leadership bid, speaking out on increasingly broad political issues and, in May, publishing a book which set out his vision for the future of France and the Socialist party.