Irish man Morgan McSweeney has resigned as British Prime Minister Keir Starmer's chief of staff, saying he took responsibility for advising him to name Peter Mandelson as ambassador to the US despite his known links to Jeffrey Epstein.

After new files revealed the depth of the Labour veteran's relationship with the late sex offender, Mr Starmer is facing what is widely seen as the gravest crisis of his 18 months in power over his decision to send Mr Mandelson to Washington in 2024.

The loss of McSweeney, a 48-year-old man from Co Cork and a strategist who was instrumental in Mr Starmer's rise to power, is the latest in a series of setbacks, less than two years after the Labour Party won one of the largest parliamentary majorities in modern British history.

With polls showing Mr Starmer is hugely unpopular with voters after a series of embarrassing U-turns, some in his own party are openly questioning his judgment and his future, and it remains to be seen whether Mr McSweeney's exit will be enough to silence critics.

The files released in the US on 30 January sparked a police investigation for misconduct in office over indications that Mr Mandelson leaked market-sensitive information to Epstein when he was a government minister during the global financial crisis in 2009 and 2010.

In a statement, McSweeney said: "The decision to appoint Peter Mandelson was wrong. He has damaged our party, our country and trust in politics itself.

"When asked, I advised the Prime Minister to make that appointment and I take full responsibility for that advice.

We need your consent to load this rte-player contentWe use rte-player to manage extra content that can set cookies on your device and collect data about your activity. Please review their details and accept them to load the content.Manage Preferences

"As I leave I have two further reflections: Firstly, and most importantly, we must remember the women and girls whose lives were ruined by Jeffrey Epstein and whose voices went unheard for far too long.

"Secondly, while I did not oversee the due diligence and vetting process, I believe that process must now be fundamentally overhauled. This cannot simply be a gesture but a safeguard for the future.

"I remain fully supportive of the Prime Minister. He is working every day to rebuild trust, restore standards and serve the country. I will continue to back that mission in whatever way I can. It has been the honour of my life to serve," added Mr McSweeney's statement.

Born in Macroom in Co Cork in 1977, Mr McSweeney departed for London at the age of 17.

He joined the Labour Party, inspired by the Good Friday Agreement, and in 2001 began working as an intern at Labour HQ.

After rising through the ranks, he became director of the think tank Labour Together in 2017, a group whose key aim was to oppose Corbynism and find a way to move the party away from the so-called 'hard left'.

Mr McSweeney was appointed head of political strategy after Labour's ascension to government in 2024, an election victory in which Mr McSweeney's role was widely lauded.

He had held the role of chief of staff since October 2024, when he was handed the job following the resignation of Sue Gray after a row over pay and donations.

In a statement, Mr Starmer said it was an "honour" to work with Mr McSweeney, saying the Cork man had "turned our party around after one of its worst ever defeats" and that he "played a central role running our election campaign".

"It is largely thanks to his dedication, loyalty and leadership that we won a landslide majority and have the chance to change the country.

"Having worked closely with Morgan in opposition and in government, I have seen every day his commitment to the Labour Party and to our country. Our party and I owe him a debt of gratitude, and I thank him for his service," Mr Starmer added.

It's about time. But once again with this PM it’s somebody else’s fault: "Mandelson lied to me" or "Morgan advised me". Keir Starmer has to take responsibility for his own terrible decisions. But he never does. https://t.co/KvVIhUmK6v

Tory leader Kemi Badenoch welcomed Mr McSweeney's departure, but said the Prime Minister should "take responsibility" for his actions.

She said on X: "It’s about time.

"But once again with this PM it’s somebody else’s fault: 'Mandelson lied to me’ or ‘Morgan advised me’.

"Keir Starmer has to take responsibility for his own terrible decisions. But he never does."

As predicted McSweeney has gone. Labour are just continuing the chaos we saw under the Tories. My money says Starmer won't be far behind after Labour’s disaster in the elections this coming May.

Leader of Reform UK Nigel Farage meanwhile said Mr Starmer will be out of No 10 soon.

The Reform UK leader said on X: "As predicted McSweeney has gone. Labour are just continuing the chaos we saw under the Tories.

"My money says Starmer won't be far behind after Labour’s disaster in the elections this coming May."

Read more: Who is Starmer's Irish adviser at centre of Mandelson scandal?

Many Labour members of parliament had blamed Mr McSweeney for the appointment of Mr Mandelson and the damage caused by the publication of the exchanges between Epstein and Mr Mandelson. Others have said Mr Starmer must go.

One Labour politician, speaking on condition of anonymity, said Mr McSweeney's resignation had come too late: "It buys the PM time, but it's still the end of days."

Mr Starmer sacked Mr Mandelson as ambassador in September over his links to Epstein.

The government agreed last week to release virtually all previously private communications between members of his government from the time when Mr Mandelson was being appointed.

That release could come as early as this week, creating a new headache for Mr Starmer just as he hopes to move on.

If previously secret messages about how London planned to approach its relationship with Donald Trump are made public it could damage Mr Starmer's relationship with the US President.

It is unclear who would replace Mr McSweeney. Vidhya Alakeson, who worked closely with Mr Starmer in opposition, is the prime minister's deputy chief of staff.

© RTÉ 2026. RTÉ.ie is the website of Raidió Teilifís Éireann, Ireland's National Public Service Media. RTÉ is not responsible for the content of external internet sites.

Images Courtesy of Getty Images.

Morgan McSweeney, who is from Co Cork, said he decided to resign after \u0027careful reflection\u0027

\u003Cp\u003EMorgan McSweeney seen arriving at the Lord Mayor\u0027s Banquet at the Guildhall in the City of London\u003C/p\u003E

\u003Cp\u003EKeir Starmer said it was an \u0022honour\u0022 to work with Morgan McSweeney\u003C/p\u003E