Sadiq Khan wins Blairite Baroness Oona King's support in race to be London mayor

Mr Khan is believed to have received backing from Baroness Oona King, the former MP for Bethnal Green & Bow

Sadiq Khan is believed to be backed by Oona King, the former MP (PA)

Left-leaning London mayoral candidate Sadiq Khan is understood to have gained the support of a leading Blairite, as he builds a “big tent” of support to win the Labour nomination.

Former Olympics minister Tessa Jowell is the current favourite to win the nomination, but Mr Khan is believed to have received backing from Baroness Oona King, the former MP for Bethnal Green & Bow. Mr Khan ran Ed Miliband’s leadership campaign in 2010 and also led Labour’s 2015 election efforts in the capital, which proved to be one of the party’s few areas of success.

A source close to Mr Khan’s campaign said: “It’s a big deal that a Blairite would support Sadiq. These are the sort of big tents that need building [to win the nomination].”

Baroness King had previously been tipped as a candidate herself, and unsuccessfully challenged Ken Livingstone for the 2012 nomination. But Mr Khan and Baroness King were spotted together last week in a coffee shop at Portcullis House, the MPs’ office block that is situated next to Parliament.

Previously chief diversity officer at Channel 4, Baroness King could have a prominent role and bring some additional media savvy to Mr Khan’s campaign, though it is understood she is unlikely to be unveiled as a possible deputy mayor. She could also help sway Blairites to vote for Mr Khan – the natural home for their votes is Ms Jowell, given that she once said she would “jump under a bus” for Tony Blair.

Liberal Democrats are urging Vince Cable, the former business secretary who lost his south-west London seat of Twickenham in one of the biggest shocks of the election, to stand for mayor. Mr Cable is considering his career options, but is thought to be concerned that the party is in too weak a state to fight an effective campaign.

Lib Dem members are also considering Lynne Featherstone, the popular former home office minister who failed to see off a Labour onslaught in the north London seat of Hornsey & Wood Green. Maajid Nawaz, who contested Hampstead & Kilburn in north London, is seen as a third possible contender.