The future of Labour’s leadership has been plunged into deeper doubt following Wes Streeting’s resignation as health secretary and confirmation that Greater Manchester mayor Andy Burnham is eyeing a return to Westminster .

On Thursday, Makerfield MP Josh Simons said he is willing to give up his seat to allow Mr Burnham the chance to win a by-election, return to parliament, and challenge the prime minister, Sir Keir Starmer .

He said that the Labour Party “owes it to people to come back together” following last week’s defeat in the local elections.

It came just hours after Mr Streeting sent a blistering resignation letter to Sir Keir, saying: “Where we need vision, we have a vacuum. Where we need direction, we have drift.”

These developments follow days of mounting questions over the prime minister’s position and the prospect of a leadership challenge following dismal local election results last week .

But how could a leadership contest be triggered, what would it look like, and who could stand?…