Nicky Gavron will work with Ken Livingstone for the next four years

Nicky Gavron was the official Labour candidate until Mr Livingstone was readmitted to the Labour Party and allowed to run as mayor.

Ms Gavron had been his running mate before he was re-elected on Friday.

She will work on environment policies, women's issues in the capital and advise the mayor on planning decisions.

'Interests of Londoners'

Last December, Ms Gavron announced that she would step down as Labour candidate for mayor, after a meeting at Downing Street with the Prime Minister Tony Blair and Labour chairman Ian McCartney.

She said she had sacrificed her place as the party's official candidate in "the interests of Londoners and re-uniting the Labour vote in London".

Mr Livingstone became Labour's official candidate in February after he was expelled for five years for running as an independent against Labour in the 2000 election.

He won the June 2004 election ahead of Tory rival Steve Norris.