Sadiq Khan has endorsed Keir Starmer in the Labour leadership contest, in a further boost to the frontrunner’s campaign.

The London mayor said Starmer was “the best person to unite our party” and “take the fight to the Tories”.

Starmer said he was “honoured” to have received Khan’s support. “Sadiq is demonstrating that Labour in power can change lives,” he said.

Khan backed Owen Smith over Jeremy Corbyn in the 2016 leadership contest and has been critical of the outgoing leader.

In an interview with HuffPost UK on Tuesday, Starmer told Labour members the “bigger the win” he had in the contest to replace Corbyn the better.

Voting in the contest began on Monday, amid a largely cordial campaign between Starmer, Rebecca Long-Bailey and Lisa Nandy.

All three on Sunday said they would offer the losing leadership candidates jobs in their shadow cabinet.

Starmer is the clear frontrunner, having won more than double the amount of local Labour party support than second-placed Long-Bailey.

And he performed the strongest in winning the support of unions and affiliated socialist organisations.

Party members will also select a new deputy leader between candidates Angela Rayner, Dawn Butler, Ian Murray, Rosena Allin-Khan and Richard Burgon.

The candidates in both contests have nearly six weeks to secure the votes of members before the ballot closes. The winners will be named on April 4.