Sir Keir Starmer has joined Tulip Siddiq, his Camden colleague in Parliament, in backing Labour MP Sadiq Khan to become the party’s candidate for next year’s London mayoral election.

Ham & High: Sadiq Khan. Picture: PA.Sadiq Khan. Picture: PA. (Image: PA Wire/Press Association Images)

The Holborn and St Pancras MP, who replaced retired veteran Frank Dobson at May’s general election, has thrown his support behind Mr Khan’s bid to be selected as Labour’s candidate to replace outgoing mayor Boris Johnson.

Tooting MP Mr Khan is considered a frontrunner for the Labour selection alongside former Labour minister and Highgate resident Dame Tessa Jowell.

Hornsey and Wood Green MP Catherine West is backing her parliamentary neighbour David Lammy, the Tottenham MP, who is also standing for Labour selection.

Sir Keir, the former director of public prosecutions, and Mr Khan are both former human rights lawyers.

Writing in the New Statesman, Sir Keir said he wanted to see Mr Khan become “the most powerful Labour politician in the country”.

Sir Keir, whose father was a toolmaker and whose mother was a nurse, also noted Mr Khan’s humble beginnings.

He wrote: “Sadiq is a Londoner born and bred. His parents were immigrants from Pakistan in the 1960s.

“His dad drove a bus and his mum worked as a seamstress. Like so many waves of migrants before them, they came to this city to make a better life for them and their family.

“As a dynamic human rights lawyer, Sadiq made his name rooting out injustice and righting wrongs. He was never afraid to take on powerful vested interests in the government, the police or the prison service. This is precisely what we need in a mayor.

“Winning next year’s mayoral contest would make this the most powerful Labour politician in the country.

“Sadiq is ideally placed to take on this role and he has the experience to stand up for Londoners against the worst excesses of the Tory government.

“He’ll bring a decency and fairness that is all too lacking in many of today’s frontline politicians.”

In June, Hampstead and Kilburn MP Tulip Siddiq endorsed Mr Khan as the candidate who “reflects all that is good about modern and diverse London”.

Mr Khan now has endorsements from 15 London MPs, more than any of the other Labour candidates.

He is standing to be selected as the party’s candidate to contest the mayoral election on May 5 next year alongside Labour MPs Mr Lammy, Diane Abbott and Gareth Thomas, as well as Dame Tessa and journalist Christian Wolmar.

Ballot papers for the Labour selection will be dispatched to members on Friday. The ballot closes on September 10 and results will be announced on September 13.