Keir Starmer's leadership has been significantly challenged by the resignation of his closest adviser and chief of staff, Morgan McSweeney. This departure follows intense scrutiny and anger regarding the controversial appointment of Peter Mandelson as US ambassador, particularly given Mandelson's ongoing association with Jeffrey Epstein. McSweeney, widely regarded as the architect of Starmer’s political ascent and a powerful yet divisive figure within Labour, publicly accepted “full responsibility” for advising the prime minister on the appointment. He conceded that his advice had ultimately “undermined trust in Labour and in politics itself.”

McSweeney's decision to step down, made on Sunday after days of pressure and private discussions with Starmer, represents a substantial blow to the prime minister. While some of Starmer's allies hoped the move would placate mounting anger among Members of Parliament and deter potential leadership challengers, senior Labour sources suggest McSweeney’s exit leaves Starmer “dangerously exposed.” This vulnerability is particularly pertinent as Starmer faces upcoming policy and electoral hurdles, including the crucial Gorton and Denton byelection. A source close to Downing Street emphasized that Starmer had “lost his firewall,” indicating that the criticism previously absorbed by McSweeney would now directly target the prime minister.

The core of the controversy lies in the decision to appoint Mandelson despite his well-documented connections to Epstein. Insider reports suggest that the Cabinet Office’s propriety and ethics team had cautioned against the appointment, citing serious reputational risks. In his resignation statement, McSweeney openly stated that the decision to appoint Mandelson was “wrong” and called for a “fundamental overhaul” of the vetting procedures for appointments, asserting that “responsibility must be owned when it matters most.”

Reactions within the Labour party to McSweeney's resignation are sharply divided. Supporters view McSweeney as a “political genius” instrumental in overturning the hard left, propelling Starmer to leadership, and securing Labour's “historic landslide election victory of 2024.” They argue his resignation underscores his commitment to protecting the prime minister, even though Starmer made the final decision. Many expressed an “immense debt of gratitude” to McSweeney for his singular role in restoring Labour's “electability” and guiding the party into government.

Conversely, many Labour MPs, especially those critical of Starmer, interpret McSweeney's resignation as symptomatic of deeper systemic issues within the leadership. Some believe that Starmer’s acceptance of the resignation, rather than an outright dismissal, portrays the prime minister as “even weaker” and risks him being implicated in McSweeney’s downfall. Critics have accused McSweeney of overseeing a “male-dominated cabal” within Downing Street that sidelined elected members and prioritized internal factional conflicts over effective governance. His advocacy for Mandelson was seen by some as an act of favoring personal connections and political allies over the best interests of the prime minister. Further concerns were raised about a “pattern of pretty indefensible behaviour,” with reference to a Labour Together investigation into journalists reporting on its funding – an organization McSweeney once led. Clive Lewis, the Labour MP for Norwich South, commented that McSweeney’s departure should not be misconstrued as a “cleansing moment,” but rather as a manifestation of a pervasive “political culture that has dominated Labour for a generation,” nurtured under figures like Blair and Mandelson, which he characterized as being “relaxed about extreme wealth” and “detached from the lives of the people it was created to represent.”

The pressure on Starmer is anticipated to intensify, particularly with the imminent release of hundreds of thousands of documents, including private communications between Mandelson, No 10 officials, and ministers during his tenure in Washington. This release could potentially expose further details about the decision-making process. Political adversaries, including Conservative leader Kemi Badenoch, have demanded that Starmer “take responsibility” for his “terrible decisions” instead of deflecting blame.

While McSweeney’s departure may provide short-term relief, especially for groups like the Tribune MPs who had called for his removal, it simultaneously removes a critical buffer for Starmer. Without his long-standing consigliere, Starmer will inevitably bear a greater burden of accountability for any future political setbacks, such as losses in upcoming local elections. Speculation about his leadership is already at a “fever pitch,” with some left-wing backbenchers foreseeing Starmer’s eventual downfall, branding him a “coward who refuses to take responsibility for his own actions” and “a moral gravity-well.”

In his official statement, Starmer acknowledged an “immense debt of gratitude” to McSweeney, crediting him with revitalizing the party after a significant defeat and for his pivotal role in securing the landslide majority. Just days prior, Starmer had publicly expressed confidence in McSweeney. This resignation makes McSweeney the second Downing Street chief of staff to leave under Starmer, following Sue Gray’s departure in 2024, highlighting a notable trend of staff turnover in No 10. McSweeney reportedly plans to temporarily withdraw from politics, though close associates anticipate his eventual return to public life.

This ongoing crisis leaves Keir Starmer in a highly precarious position, facing intensified scrutiny over his judgment and leadership capabilities, with the repercussions of the Mandelson appointment and the loss of his key strategist poised to significantly shape his immediate political trajectory.