Labour have launched the search for a candidate to take on Boris Johnson in the 2012 London mayoral election.

Ken Livingstone, who was in charge at City Hall for eight years before being ousted by the flamboyant Tory in 2008, has signalled he will throw his hat in the ring.

Other challengers, who have until June 18 to put their names forward, are expected to include former Bethnal Green and Bow MP Oona King, who lost her seat to Respect's George Galloway.

Hopefuls will be whittled down to a shortlist by a panel of national and London party representatives on June 24 before a series of hustings across the capital. An electoral college, made up half-and-half of votes by London party members and members of affiliated organisations, will then pick the candidate.

The result will be announced on September 22 - the day before the party reveals who has won the race to succeed Gordon Brown as national party leader.