Who is Morgan McSweeney? Starmer’s right-hand man and Peter Mandelson ally

Morgan McSweeney has resigned as Keir Starmer’s chief of staff – taking “full responsibility” for advising the prime minister to appoint Peter Mandelson as US ambassador.

It comes as Sir Keir faces mounting pressure to resign amid controversy of Lord Mandelson’s links to the disgraced financier and paedophile Jeffrey Epstein.

McSweeney, credited with masterminding Labour’s landslide election victory in 2024, was considered the driving force behind Lord Mandelson’s appointment.

His resignation has been interpreted by many as a damage limitation exercise in a bid to save Mr Starmer’s premiership.

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McSweeney is alleged to have had knowledge about Mandelson's dealings with Epstein continuing after the financier’s conviction for child sex offences.

As the prime minister’s right-hand man, Mr McSweeney was central to government strategy and decision-making.

He was consequently seen by some as responsible for Downing Street’s failed attempt to control the release of potentially explosive documents detailing the appointment decision.

“The decision to appoint Peter Mandelson was wrong,” he wrote in a statement on Sunday announcing his resignation. “He has damaged our party, our country and trust in politics itself.”

In the letter McSweeney called for an overhaul of the vetting system, writing: “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.”

Mr McSweeney was born in County Cork but left Ireland for London in 1994 aged 17, where he is said to have initially worked on building sites.

He joined the Labour Party in 1997, reportedly motivated by the backing for the Good Friday Agreement which was key to the Northern Ireland peace process.

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In June 2001, he took a job as a Labour conference administrator, according to his Linkedin profile.

Reports suggest he was later hired to work in Labour’s “attack and rebuttal unit” in the party’s Millbank headquarters, where he is said to have been tasked with adding information to Peter Mandelson’s “excalibur” database which informed campaign messaging.

He is also said to have been sent to marginal seats to campaign during the 2005 general election, as his reputation as an effective organiser and operator began to grow.

He was viewed as a key figure in a successful push, led by the current Communities Secretary Steve Reed, to oust the coalition of Liberal Democrats and Conservatives in the London borough of Lambeth.

After failing in a bid to become a councillor in Sutton in 2006, he was appointed head of Mr Reed’s leader’s office in Southwark, a role he held until October 2007.

After a stint as the director of communities at The Campaign Company consultancy, Mr McSweeney joined the Local Government Association as a political adviser and was later appointed head of the organisation’s Labour group office, a position he held until 2017.

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During that time, he ran Liz Kendall’s leadership campaign in 2015 which resulted in the current Science Secretary finishing fourth.

Mr McSweeney was appointed director of the Labour Together think tank in 2017, sharing a place on the board with Mr Reed and current Culture Secretary Lisa Nandy.

At the time he is said to have declared his intention to move the party, then led by Jeremy Corbyn, “from the hard left” and “build a sustainable winning electoral coalition”.

But later Mr McSweeney came under scrutiny over financial irregularities during his role at Labour Together.

In 2021, the Electoral Commission fined the think tank £14,250 for failing to deliver donation reports within 30 days, inaccurately reporting donations and failing to appoint a responsible person within 30 days of accepting a donation.

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The Conservatives called for the regulator to revisit the case in September last year after emails, seemingly sent by a Labour Together lawyer to Mr McSweeney, were leaked.

Despite the Conservative Party chairman Kevin Holinrake suggesting the emails could serve as evidence that the Electoral Commission had been misled, the regulator said a review of the information had not provided “evidence of any other potential offences”.

Mr McSweeney was appointed to run Sir Keir’s successful 2020 leadership campaign and initially became his chief of staff.

But following a poor Labour showing in the Chesham and Amersham by-election in 2021, he was moved to a strategic role in the leader’s office but is said to have remained a key adviser.

After being appointed as Labour’s director of campaigns in September 2021, Mr McSweeney is said to have been behind a push to impose a new centralised long-listing of parliamentary candidates, a process considered as an attempt to lock out those on the left of the party.

Labour’s election victory in 2024 resulted in Mr McSweeney being appointed to the shared role of head of political strategy.

Reports later suggested tension had developed between Mr McSweeney and then chief of staff Sue Gray but Labour sources provided contradictory opinions on the relationship at the time.

Following Ms Gray’s resignation, Mr McSweeney was appointed Downing Street chief of staff in October 2024.

Mr Starmer said of his resignation: “It’s been an honour working with Morgan McSweeney for many years. He turned our party around after one of its worst ever defeats and played a central role running our election campaign.”