Ed Miliband has told Cabinet colleagues he will challenge Wes Streeting if the Health Secretary launches a bid to replace Sir Keir Starmer as Prime Minister.

The Energy Secretary, who served as Labour leader from 2010 to 2015, consistently comes out on top when Labour members are asked to rank members of the Cabinet.

Mr Miliband’s leadership ambitions have been regularly brought into question, particularly after a lukewarm response to bombshell revelations about Lord Mandelson.

The Doncaster North MP is understood to be backing Andy Burnham if Sir Keir is forced out of No10.

Mr Miliband is telling friends he does not want the Labour leadership and would rather become “kingmaker” for Mr Burnham.

However, two insiders have told The Times that Mr Miliband would stand as the soft-left’s candidate to stop Mr Streeting winning the keys to No10.

A source close to the Energy Secretary said: “This is mischief-making – it is categorically untrue that Ed told Cabinet colleagues that he was preparing to stand in case of a contest.”

Sir Keir is also expected to face a showdown with Mr Streeting in No10 tomorrow, with the Health Secretary expected to discuss the “turbulence” gripping the Labour Party and how the Prime Minister expects to “get us out of this mess”.