Morgan McSweeney, the mastermind behind Sir Keir Starmer’s rise to power as Labour leader and Prime Minister, has resigned as the Downing Street Chief of Staff.
The departure comes after controversy over the decision to appoint Peter Mandelson as the UK’s ambassador to the US flared back up following the latest Epstein files release.
Lord Mandelson is believed to have acted as a mentor to McSweeney, who was reportedly the driving force behind the appointment in December 2024.
The choice proved to be catastrophic, with Mandelson – a top figure in Labour for four decades – lasting just seven months in the post.
He was fired in September after documents released in an earlier batch of files exposed the true extent of his close friendship with convicted sex offender Jeffrey Epstein.
The slow-burning disaster led to Mandelson losing not only his job but his seat in the House of Lords and membership of the Labour Party – and caused an enormous amount of damage to an already weak Starmer.
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With some Labour MPs calling for the Prime Minister to step down over the scandal, it appears McSweeney has instead taken the blame.
But it is unclear whether the move will be enough to keep the wolves from the door of No 10.
In a statement, McSweeney said: ‘After careful reflection, I have decided to resign from the government.
‘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.
‘In public life responsibility must be owned when it matters most, not just when it is most convenient. In the circumstances, the only honourable course is to step aside.’
McSweeney, 48, is widely regarded as the single most powerful and influential backstage figure in today’s Labour Party.
His strong professional relationship with Mandelson is believed to have started around 2017, when McSweeney set up a think tank that pushed for a purge of Jeremy Corbyn supporters from Labour.
Mandelson was reportedly a key figure in subsequently helping him forge the path to the party’s 2024 election landslide.
According to the Telegraph and New Statesman, the then-peer was a frequent visitor to McSweeney’s home in the west of Scotland, and even provided advice for last year’s Cabinet reshuffle.
Mandelson is quoted as saying of the strategist: ‘I don’t know who and how and when he was invented, but whoever it was they will find their place in heaven.’
In the meantime, McSweeney had engineered Sir Keir Starmer’s victory in the 2020 Labour leadership contest and remained a top adviser after his boss became PM.
After three months as joint-head of political strategy in Downing Street, he consolidated power by taking over as Chief of Staff when Sue Gray was forced out of the position.
His immense power behind the scenes often made him a target of contempt for MPs on the left of the party.
But the extent of his influence over the PM will now lead to questions about what Downing Street under Keir Starmer will look like without him.
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