Sadiq Khan, the son of a bus driver, became London's first Muslim mayor on Friday, seeing off a Conservative challenger who attempted to link him to extremism and securing a much-needed victory for his opposition Labour Party.

As New York mayor Bill de Blasio sent his congratulations, Khan had yet to receive official notification of his victory, which would go some way to soothing the wounds of Labour which suffered losses in Thursday's other local elections.

Dealt a crushing blow in Scotland, where it came third behind the Scottish National Party and Britain's ruling Conservatives, Labour did better than expected in England, saving its left-leaning leader from an early challenge.

But the big prize was the London mayor vote, which pitted Khan, 45, who grew up in public housing in inner city London, against Conservative Zac Goldsmith, 41, the son of a billionaire financier.

A source close to the count said Khan could not now be beaten in the race.