The architect of Keir Starmer’s ascent to power has fallen. Morgan McSweeney, the Downing Street Chief of Staff credited – and by some, blamed – for Labour’s remarkable turnaround, has resigned, a move steeped in the fallout from a deeply damaging scandal.
The crisis centers on Peter Mandelson, the veteran Labour figure whose appointment as the UK’s ambassador to the US ignited a firestorm. Renewed scrutiny of the Epstein files has brought long-held concerns about Mandelson’s association with the convicted sex offender back into sharp focus, ultimately proving fatal to his diplomatic career and now, to McSweeney’s position.
McSweeney, 48, is understood to have been a mentor to Mandelson, and was the driving force behind the controversial ambassadorial appointment in December 2024. That decision, now widely viewed as a catastrophic error in judgment, led to Mandelson’s dismissal after just seven months, the loss of his seat in the House of Lords, and expulsion from the Labour Party.
In a starkly worded statement, McSweeney accepted full responsibility. “The decision to appoint Peter Mandelson was wrong,” he declared. “He has damaged our party, our country and trust in politics itself. I advised the Prime Minister to make that appointment and I take full responsibility for that advice.” He framed his resignation as the only honorable path forward, a demonstration of accountability in a political landscape often criticized for its lack of it.
The departure sends shockwaves through Westminster, raising serious questions about the future of Starmer’s premiership. McSweeney wasn’t merely an aide; he was the strategic force behind Labour’s dramatic shift from electoral wilderness to Downing Street. Accounts of the party’s post-Corbyn rebuild consistently point to McSweeney as the architect who identified Starmer as the leader capable of restoring credibility.
He is credited with steering the party towards the center, influencing policy on issues like immigration and welfare, and shaping the composition of Starmer’s Cabinet, with allies like Shabana Mahmood and Steve Reed holding key positions. His influence was so pervasive that some question whether Starmer can effectively lead without the strategist by his side.
While McSweeney’s resignation may quell immediate calls for Starmer’s own head, the long-term implications are far from certain. Some speculate that Starmer might now feel freer to pursue more left-leaning policies, a return to the principles he espoused during his 2020 leadership campaign. However, the more pressing concern is the potential for a destabilized Downing Street operation, lacking the steady hand that guided it to power.
Starmer himself acknowledged McSweeney’s pivotal role, stating, “He turned our party around after one of its worst ever defeats and played a central role running our election campaign.” He expressed deep gratitude for McSweeney’s dedication and loyalty, recognizing the debt the party and he personally owed him.
The opposition has been quick to capitalize on the turmoil. Conservative leader Kemi Badenoch accused Starmer of a familiar pattern of deflecting blame, stating he “never does” take responsibility for his own decisions. The resignation has opened a new front in the political battle, highlighting the fragility of power and the enduring consequences of poor judgment.
McSweeney’s rise began around 2017, with the establishment of a think tank aimed at purging Corbyn supporters from the Labour Party. Mandelson reportedly played a crucial role in his ascent, offering guidance and support, even visiting McSweeney’s home in Scotland to advise on Cabinet reshuffles. Mandelson himself once described McSweeney as someone destined for “a place in heaven,” a sentiment that now rings with bitter irony.
Having engineered Starmer’s 2020 leadership victory and subsequently served as Chief of Staff, McSweeney’s influence was undeniable, though often resented by those on the left of the party. His departure leaves a void at the heart of the government, forcing a reckoning with the question of what a Starmer premiership will look like without the man who built it.
