Morgan McSweeney, the strategist who engineered Labour’s turn from activism to authority and shepherded Keir Starmer to Downing Street, is facing the most bruising test of his quiet power. The prime minister’s chief of staff has been pulled into the fallout from the appointment of Peter Mandelson as U.K. ambassador to the United States, a decision now tainted by Mandelson’s continued association with convicted sex offender Jeffrey Epstein. Starmer has apologized to Epstein’s victims and for “believing [Mandelson’s] lies,” while insisting he retains full confidence in McSweeney.
For a figure with almost no public profile — few videos, even fewer on-the-record remarks — the 48-year-old Cork native has long had an outsized reputation inside Labour. The News Agents podcast once dubbed him “the most powerful man in politics,” reflecting the belief that McSweeney authored Labour’s strategic reset and curated Starmer’s rise. He is closely associated with the party’s shift toward a socially conservative, “Blue Labour”-inflected pitch centered on patriotism, order and incremental reform.
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His current jeopardy stems from proximity to a choice that has rapidly become a moral and political liability. While it has not been confirmed, it has been widely reported that McSweeney played a key role in Mandelson’s selection. Allies argue both he and Starmer were misled. Housing Secretary Steve Reed, who has worked with McSweeney for nearly two decades, said the pair were “not at fault” and were lied to over the extent of Mandelson’s relationship with Epstein. “You’re only as good as the information you receive,” Reed said. Backbench critics are unforgiving: one Labour MP, speaking anonymously, said McSweeney “needs to go” and accused him of self-interest.
The dispute lands at the heart of how No. 10 now works — and who, inside it, sets the tempo. McSweeney’s skill has been gatekeeping: picking the fights Labour avoids, framing the ones it takes, and stress-testing every move against the single metric that has defined Starmerism — credibility. As director of the Labour Together think tank from 2017, he channeled a broad anti-Corbyn coalition into a plan to reclaim electability. Journalists Patrick Maguire and Gabriel Pogrund report that McSweeney and allies effectively decided Starmer was the figure to deliver that project, “handpicking” him as the 2020 leadership candidate to face the party’s hard left. From that point, McSweeney’s fingerprints were everywhere.
He urged a patriotic rebrand — Union Flags on party materials and “God Save the King” sung at conference — to signal a rupture with the recent past. Inside opposition, he was Starmer’s first chief of staff, later shifted into a strategic role after a by-election stumble. After Labour’s 2024 general election victory, McSweeney formally became head of political strategy. In October 2024, he was elevated to Downing Street chief of staff after Sue Gray resigned amid a row over her pay.
His ascent has never been tidy. Labour Together was fined £14,250 in 2021 for failing to declare donations within the 30-day window. The issue flared again last year when Conservative Party chairman Kevin Hollinrake asked the Electoral Commission to reopen an inquiry, accusing McSweeney of running a “secret slush fund” to install Starmer. Regulators declined to launch a new investigation. That skirmish added to a swirl of intrigue over anonymous briefings that alleged Health Secretary Wes Streeting harbored leadership ambitions — claims both Starmer and Streeting said did not originate from Downing Street, with Streeting affirming confidence in McSweeney.
Understanding why the Mandelson episode matters requires a look at how McSweeney sees politics. His approach prizes message discipline and the optics of responsibility. The Starmer project — tough-minded on spending, rigorous on standards, allergic to grandiosity — was designed to inoculate Labour against charges of recklessness. Choosing Mandelson, a totem of Labour’s modernizing past and a seasoned operator in Washington circles, followed that logic on paper: appoint a known quantity to a crucial post in America. But the decision has collided with the party’s pledges on ethical probity and reopened old arguments about Labour’s relationship with a pre-crash establishment.
That clash is why the blame is so pointed. Even if McSweeney and Starmer were misled, critics say the vetting should have caught the risk. The apparent misjudgment corrodes a core promise: that this administration is hard-headed enough to avoid avoidable trouble. For a strategist whose value lies in anticipating reputational hazards, it is a withering charge.
Yet McSweeney’s durability reflects more than proximity to the prime minister. He has been the organizing mind behind Labour’s electoral rebuild and a broker among its feuding tribes. Allies of “Blue Labour” see his influence in the party’s language on work, community and security. Soft-left pragmatists credit him with the painstaking assembly of a de-risked policy platform. Even many who dislike the path concede McSweeney turned a fractious movement into a winning machine. That machinery — and the tight circle that runs it — is not easily redesigned mid-term.
His biography underscores a career forged in the engine room rather than at the dispatch box. Born in Macroom, County Cork, in 1977, he moved to London at 17, worked on building sites, dropped out of university within a year, then spent six months on an Israeli kibbutz. He returned to study politics and marketing at 21, joined Labour inspired by the Good Friday Agreement, and in 2001 started as an intern at party headquarters. By 2006 he was sharpening his campaign craft alongside Steve Reed in Lambeth, helping wrest control of the council against a national tide running blue. He worked on anti–British National Party efforts and ran Liz Kendall’s doomed 2015 leadership bid — proof that he knows defeat as well as victory.
The portrait that emerges is of a guarded operator who prefers spreadsheets to speeches, a political technologist who saw where Labour needed to go and created the structures to get there. His adversaries bridle at his unaccountable sway; his advocates insist that, without him, there would be no Starmer government to defend.
What happens next will be a study in how power is held and spent. Starmer’s apology over Mandelson draws a bright ethical line. His continued backing of McSweeney signals he is not prepared to let adversaries pick off his lieutenants — at least not yet. Whether that stance holds may depend on what else emerges, how quickly the U.S. ambassadorial question is resolved, and whether No. 10 can close the gap between the government’s rhetoric on integrity and the processes it uses to make high-stakes appointments.
Inside Labour, the episode will intensify debates that McSweeney has managed for years: between professionalized politics and movement energy; between reaching voters where they are and respecting the party’s moral instincts. If he weathers the storm, it will be because he convinces colleagues that the strategic compass remains true and that lessons have been learned in the only currency that counts to him — competence.
For all the secrecy, one fact is inescapable. Morgan McSweeney has shaped the parameters of British politics more than any adviser in a decade. The question now is whether the architect of Starmerism can still guarantee what he once delivered: no unforced errors, and a government that looks like it knows exactly what it’s doing.
By Abdiwahab Ahmed
Axadle Times international–Monitoring.
