Ruth Jones said Sir Keir had been "wounded" by the scandal over his decision to appoint Peter Mandelson as US ambassador last year, but did not know if it would be "fatal" for his time as prime minister.

Jones spoke before Scottish Labour leader Anas Sarwar called for Sir Keir to resign over the scandal on Monday.

BBC Wales understands First Minister Eluned Morgan is not expected to do the same - despite previously refusing to back him - with one Welsh Labour source saying she is "not in that space".

Morgan is expected to address the matter at First Minister's Questions in the Senedd on Tuesday.

Downing Street said the prime minister had no plans to step down over his appointment of Lord Mandelson, despite the former US ambassador's relationship with convicted sex offender Jeffrey Epstein.

Welsh Secretary Jo Stevens joined a stream of cabinet ministers to publicly back Sir Keir, saying he "defied the naysayers many times and he'll do so again".

Asked if Sir Keir could survive as prime minister, Jones told Radio Wales Breakfast earlier on Monday: "I think he's wounded, absolutely. But is it fatal? I don't know. We'll wait and see."

She said the upcoming UK elections for Gorton and Denton on February 26 and then across Wales on 7 May are "critical."

"Depending on what happens there, then I think we judge the prime minister on those events and the results that the Labour party gets," she said.

Jones said Morgan McSweeney, who quit as Sir Keir's chief of staff over the scandal on Sunday, was perceived "by a lot of MPs as the power behind the throne" and "whispering into his ear".

Ordinary MPs felt he was "always blocking what we might be trying to talk to Keir about," she said.

Meanwhile an unnamed UK government minister told the BBC that McSweeney's resignation was "too little too late", describing Sir Keir's judgement as "so poor".

They described events at Number 10 as a mess and said they "honestly don't know what happens next".

"I really have a lot of respect for the PM and I believe he is a good man but his judgement has been so poor," they added.

A second Welsh Labour source told the BBC they expect Morgan to stay out of the row because Sir Keir has strong support among Welsh MPs - with most of Wales' 32 Labour MPs involved in working in the UK government in one way or another.

One Labour MP told the BBC it was "incredibly frustrating" that the first minister "hasn't been more supportive of the PM".

Opinion polling over recent months have suggested that Plaid Cymru and Reform UK are both vying to win the Senedd election. Labour came third in a by-election in Caerphilly last October, losing to Plaid.

With less than three months to go, Ruth Jones said the Labour party had a "good story to tell" in Wales ahead of the election, but that Sir Keir needed to change his approach.

"I think we need to make sure that we tell it better and I think Keir needs to engage more in Wales," she said.

"I think Keir needs to get out there to make his own pitch, because I'm not going to make it for him."

Jones said the UK party realises now "what might be coming down the track".

"They are taking it seriously now. It's been a struggle to get them to realise that," she said.

Alun Davies, who represents Blaenau Gwent in the Senedd, told BBC Politics Live that things were "terrible on the doorstep" for the Labour party, and said he didn't think Sir Keir paid enough attention to Wales and the UK beyond London.

Opposition parties rounded on the first minister for not expressing a view one way or the other.

Calling for Sir Keir to quit, Plaid Cymru leader Rhun ap Iorwerth said that by remaining silent the first minister was "seemingly happy for the chaos to continue and for the prime minister to squat in Downing Street".

Dan Thomas, Reform UK Wales leader, said: "Clearly the first minister is waiting to see which way the wind blows. This is the quality of leadership the Welsh people have come to expect from Labour."

Welsh Conservative Senedd leader Darren Millar said: "Labour's leader in Scotland has expressed a view that Kier Starmer should go. Labour's leader in Wales must have a view, she should have the courage to tell us what it is."

The Welsh Liberal Democrats said: "If Eluned Morgan isn't prepared to speak up for Wales now, it raises serious questions about whether Welsh Labour has the backbone to stand up for Wales at all."

Additional reporting: Mark Palmer and Gareth Lewis

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Sir Keir Starmer's administration appears rudderless after the loss of two key aides, writes Chris Mason.