Scottish Labour leader Anas Sarwar has called for Sir Keir Starmer to step down as prime minister.
During an emergency news conference at 2.30pm, he said: "The leadership in Downing Street has to change.
"It is so obvious that we desperately need change in Scotland and in three months time, the opportunity to get rid of a failing SNP government is one that is too important to be missed.
"We cannot allow the failures at the heart of Downing Street to mean the failures continue here in Scotland, because the election in May is not without consequence for the lives of Scots."
Mr Sarwar called Sir Keir "a decent man" and said it is "no secret that I have always got on well with him" and called him a friend, but said he needed to decide "what I'm willing to accept and what I'm willing to tolerate".
He said he is not backing any specific replacement, but said there have been "too many incidences where the wrong judgement calls have been made".
And he revealed he had spoken to Sir Keir earlier in the day, adding: "I think it's safe to say that he and I disagreed."
The Scottish Labour leader is the most senior Labour voice to call for Sir Keir to go after several backbenchers have done so following more revelations about Lord Mandelson's links to paedophile Jeffrey Epstein.
Sir Keir's leadership looks to be in freefall after his chief of staff, Morgan McSweeney - his right-hand man - resigned on Sunday over his role in appointing Lord Mandelson as ambassador to the US.
Tim Allan, his director of communications, then quit on Monday morning, saying he wants to "allow a new No 10 team to be built".
However, Sir Keir's spokesman insisted he was "upbeat and confident" and would not be resigning today.
Mr Sarwar, who is from the same wing of Labour as the PM, has so far remained quiet about his feelings on how the government is working in Westminster, but as the Holyrood elections approach in May, he appears to want to distance himself from his party's leader.
His unexpected intervention comes just hours before Sir Keir addresses his MPs at a Parliamentary Labour Party meeting in Westminster on Monday evening.
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(c) Sky News 2026: Scottish Labour leader calls for Starmer to stand down
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