We're wrapping up Politics Hub for today after the bombshell announcement that Keir Starmer top aide Morgan McSweeney has resigned as chief of staff.

Pressure over the pair's handling of the Mandelson scandal had grown too much, leaving McSweeney to take "full responsibility" for the former peer's appointment as ambassador to the US.

The prime minister asked his deputy chiefs of staff, Jill Cuthbertson and Vidhya Alakeson, to be acting chiefs of staff.

But they will be facing a difficult task to steady the ship at No 10, as several Labour MPs have put Starmer himself in the crosshairs today.

Watch political editor Beth Rigby's rundown of a momentous day in Westminster...

Two of his most outspoken critics, Kim Johnson and Brian Leishman, called on Starmer to resign.

"All this has done has bought him a little more time but he's mortally wounded and it's not if, it's when he goes," another Labour MP told Paste BN, speaking anonymously.

Later, the prime minister will address the Parliamentary Labour Party and provide an update on how the Mandelson scandal will be handled as he is fighting for his premiership.

Be sure to join us for that.

Union leaders have also weighed in on the Westminster fallout from the Mandelson revelations over the course of the day.

Most notably, Steve Wright, general secretary of the Fire Brigades Union, became one of the first senior trade union figures traditionally aligned with Labour to call for Keir Starmer to quit.

The country "needs to see change", he told the BBC. Wright argued the transformation voters expected 18 months ago "just hasn't happened - and we're just seeing a continuation of what happened before".

Asked about whether Starmer should quit, he said: "I think everybody's thinking it. We're just not saying it at the moment."

He added: "It seems that the prime minister isn't taking advice from elected people within his own government … he's listening to a factional group which are making bad decisions, it seems."

The general secretary of the RMT transport union, Eddie Dempsey, echoed the call for Starmer to resign, saying he was alienating working-class voters.

Dempsey, whose union is not affiliated with Labour, told The Telegraph: "Mandelson's association with a notorious paedophile and Starmer's decision to hire him as US ambassador could be fatal for this government unless the Labour Party changes its leadership and starts organising society in the interests of working people, rather than doffing the cap to the money markets, spivs and speculators."

Our political editor Beth Rigby has summarised what Morgan McSweeney's resignation today will mean for Sir Keir Starmer's political future.

Watch the video to see where we stand at the end of a busy Sunday in Westminster...

The fallout over Morgan McSweeney's resignation is dominating tomorrow's front pages.

Several papers question how long Sir Keir Starmer will be able to stay in office after his top aide stepped back. 

The Telegraph calls the resignation the prime minister's "last card".

Our deputy political editor Sam Coates has analysed how Morgan McSweeney's exit will affect the dynamics within the government.

"I've been talking to a cabinet minister who said the government too often conceded Keir Starmer subcontracted the politics to Morgan McSweeney," Coates said. 

"He will now have to do it on his own, and he will be able to show his team and the country that actually he knows what the British public wants and can deliver for it."

But, as the prime minister has "got rid of his very final line of defence" in McSweeney, Coates says there is a lot of pessimism out there.

Watch his analysis on the impact in the video...

Andrew Clark, the chair of Labour's local branch in Islington South and Finsbury, has spoken out against suggestions that voters want Sir Keir Starmer out after the latest Mandelson revelations.

"The message that we tend to get from voters is just get on with it," the grassroots campaigner told Paste BN. 

"When we talk to people on the doorstep, what they tend to say is they want quicker change that will impact their everyday lives," he explained.

"It's fairly unusual that we have people raise Westminster scandals of this sort. 

"And I think their concern would be that if there's a change of leadership, it would just slow down progress on all those policies."

Clark also shared his thoughts on Peter Mandelson's appointment and Morgan McSweeney's role - watch his comments in the video...

In polls conducted before today's development, a narrow majority of people who voted Labour at the last election said Keir Starmer should stay prime minister.

According to pollster YouGov, 40% wanted him to stay while 37% said he should resign.

"These are pretty bad figures," said Peter Kellner, a former president of YouGov, noting that they didn't even take into account the latest revelations about Peter Mandelson.

But he noted there is a sliver of hope for Labour as a party, as a recent poll shows their support hasn't fallen in the last couple of weeks.

He also analysed who could be the public's favourite for replacing Starmer. 

Watch his remarks in the video...

By Faye Brown, political reporter

We are continuing to hear from Labour MPs following the resignation of Morgan McSweeney.

One Labour MP, speaking anonymously, offered scathing criticism of the parting chief of staff and openly suggested it could mean the end of Sir Keir Starmer's premiership.

"I won't be shedding a tear that [McSweeney]'s gone," they said. 

"He's the very worst of our party, every decision he's taken is to bolster himself and wage a war of factionalism. 

"The PM should have sacked him just as he should have with Mandelson. 

"The buck ultimately stops with the PM. All this has done has bought him a little more time but he's mortally wounded and it's not if, it's when he goes."

'Turning point' for the party

By contrast, Patrick Hurley, the Labour MP for Southport, says the prime minister has his "full support" and believes the resignation was a "turning" point for the party.

"I’m grateful to the prime minister for getting a grip on the fact that he’s been badly advised on a range of issues over the last 18 months," he tells Paste BN.

"This is now a turning point and an opportunity to refocus on what the public want, and the promises we made when we were elected in 2024.

"The prime minister has my full support and I am sure the whole Parliamentary Labour Party will now collectively raise our game and deliver the positive changes the country needs."

Another MP blames McSweeney for 'retreat' to 'comfort zone'

Another Labour MP also welcomed McSweeney's resignation - suggesting he is to blame for many of Labour's problems over the past 18 months. 

 "The final bulwark against Labour retreating to its middle-class, progressive comfort zone...has gone," the MP said. 

'Looks like carelessness'

However, one MP was more bleak about things. "To lose one senior adviser may be regarded as a misfortune; to lose two looks like carelessness," they said, referring to the fact McSweeney replaced the short-lived Sue Gray as chief of staff.

Still 'serious questions' for PM

Rachael Maskell, who last week said there are "serious questions" for Starmer to answer over the Mandelson scandal, does not think McSweeney's resignation puts the matter to bed. 

She said: "It is right for Morgan McSweeney to leave Downing Street but his involvement in the appointment of Peter Mandelson, and with the 'kitchen cabinet' alongside Peter Mandelson with regards to our party, must not go without scrutiny."

Ayesha Hazarika, a Labour peer, has criticised the culture in government that led to Peter Mandelson's appointment, as she reacted to Morgan McSweeney's resignation.

She said she was "glad" the outgoing chief of staff, who championed Mandelson's appointment, highlighted Jeffrey Epstein's victims in his statement.

"But clearly the plight of women and girls was considered secondary to the fact that Peter Mandelson could do business with Donald Trump," Hazarika told Paste BN. 

She said the previous UK ambassador to the US, Karen Pierce, "was a very good woman" and Mandelson only got the job "because he moved in these circles of these very, very powerful men".

"I think a calculation was taken that it was in Britain's national interest to put that transactional relationship above the plight of women and girls," Hazarika said.

She also addressed whether McSweeney's resignation could ultimately save Starmer - watch her full remarks in the video...

The prime minister is set to address the Parliamentary Labour Party tomorrow, our political editor Beth Rigby has learnt.

Moreover, Sir Keir Starmer will address the Women's PLP, the caucus of female Labour MPs, on Wednesday after PMQs.

That's because Starmer knows he needs to make the case to MPs, particularly female MPs, incensed by the Mandelson affair, Rigby says.

According to the latest Epstein files release, Peter Mandelson not only shared confidential information with Jeffrey Epstein when he was the business secretary but also entertained a very close relationship with the convicted sex offender.

The files have led to questions over Starmer's judgement in appointing Mandelson to the top diplomatic position.

Mandelson denies any wrongdoing in relation to Epstein and has apologised to Epstein's victims for his association with him. 

Earlier today, Rigby had also reported that Starmer is also likely to provide an update on how the government will address issues highlighted by the Mandelson scandal.