British Prime Minister Keir Starmer's leadership was under intense pressure after a Labour MP stood aside to allow Greater Manchester Mayor Andy Burnham to attempt to return to parliament and challenge him.
Mr Burnham said he wanted to return to Westminster to "make politics work properly for people" after Josh Simons, the Labour MP for Makerfield, said he would stand down so Mr Burnham can "drive the change our country is crying out for".
Sources have said Mr Starmer will not seek to block Mr Burnham from becoming Labour's candidate in the forthcoming bye-election, but first the party's National Executive Committee needs to give him the green light to stand when it meets next week.
Earlier yesterday, Wes Streeting resigned as health secretary, while former deputy prime minister Angela Rayner revealed that she had been cleared of deliberate wrongdoing over her tax affairs, clearing the path for a potential tilt at the top job.
Mr Starmer has faced mounting calls to quit in the wake of Labour's disastrous local election results last week, prompting speculation his critics within the cabinet were prepared to tell him it was time to resign.
But by lunchtime yesterday, only Mr Streeting, who was later replaced by former chief secretary to the Treasury James Murray, had quit the Government.
However, in doing so, he had not - as some had expected - launched a leadership bid in the process, as he urged Mr Starmer to allow the "best possible field of candidates" to run to replace him in Downing Street.
It is still unclear whether Mr Streeting has the support of 81 Labour MPs as needed to launch a formal challenge against the prime minister.
By mid-afternoon yesterday, there was still no leadership challenge under way and attention turned to Mr Burnham to see whether he would launch his own challenge.
But as he announced on social media his plan to return to Westminster, Mr Burnham hinted any leadership contest should wait until he was an MP.
He said: "We owe it to people to come back together as a Labour movement, giving the prime minister and the Government the space and stability they need as the bye-election takes place."
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That announcement came within minutes of Mr Simons, a former Starmer loyalist who quit as a minister in February amid controversy over a think tank he used to run, calling for a "change in leadership" as he announced he would stand down as an MP for Mr Burnham.
While some 89 MPs have so far publicly called for Mr Starmer's esignation, they are not united behind a single candidate to replace him.
If he did not step down, Mr Starmer would automatically be on the ballot paper in any race, and Downing Street has continued to insist that he would fight any effort to oust him.
Mr Streeting's is the first departure from the cabinet, after the resignations on Tuesday of junior ministers Jess Phillips, Zubir Ahmed, Alex Davies-Jones and Miatta Fahnbulleh.
Armed forces minister Al Carns and Energy Secretary Ed Miliband have also been tipped as potential leadership candidates.
