Sadiq Khan urges progressives to back him amid concern about new voting system

The London mayor fears most voters are unaware of the change to a first past the post system that may boost the Tory candidate

Sadiq Khan has warned progressive voters that they risk handing the London mayoralty to an increasingly rightwing" Tory party unless they back Labour, amid concern in his camp that most Londoners are unaware of a complete overhaul of the voting system.

The battle for control of City Hall next May will be the first mayoral contest to switch to the first past the post voting system. It comes after a legal change last year that appears to be largely unknown among the capital's voters. The previous system allowed voters to pick their second preference.