A Daily Mail columnist said Prime Minister Keir Starmer must publicly explain what he knew and when he learned it about Peter Mandelson’s links to convicted sex offender Jeffrey Epstein, and suggested resignation if Mr. Starmer cannot do so.

In a column published Wednesday, Dan Hodges set out a series of questions he said the prime minister must answer as controversy over Mandelson, Britain’s ambassador to Washington, mounted. Hodges described recent reporting, including what he called a leaked email from Mandelson to Epstein, as undermining Mr. Starmer’s defence of his ambassador.

At Prime Minister’s Questions on Tuesday, Mr. Starmer expressed confidence in Mandelson and said the ambassador had repeatedly expressed regret for his association with Epstein. Conservative leader Kemi Badenoch pressed Mr. Starmer to “cut Mandelson adrift,” according to the column, but Hodges said the prime minister repeatedly defended his envoy.

The column cites what it described as a leaked email from Mandelson to Epstein that, it reported, contained lines in which the ambassador said: “I think the world of you and I feel hopeless and furious about what has happened” and urged Epstein to “be incredibly resilient, fight for early release and be philosophical about it as much as you can.” The Daily Mail presented the email as newly revealed material; the contents have not been independently verified by other outlets in reports citing Hodges’ column.

Hodges also wrote that a Cabinet Office memo detailing an attempt by Mandelson to arrange a meeting between then-prime minister Tony Blair and Epstein was suppressed on the grounds publication could damage UK–US relations. The column said that a separate memo from Lord Glasman, produced after Donald Trump’s inauguration and forwarded to Mr. Starmer’s senior adviser Morgan McSweeney, warned that Mandelson’s appointment risked provoking senior figures in Washington and recommended withdrawing the ambassador.

Hodges argued that the emerging details raise three potential explanations for Mr. Starmer’s remarks at the despatch box: that he did not ask Mandelson about the allegations; that he asked and was misled; or that Mandelson refused to provide a full account. The columnist said each scenario, if true, would make Mr. Starmer “not fit to remain in office.” Hodges reiterated Mr. Starmer’s pre-election pledge to “restore standards in public life” and urged the prime minister to provide a “unequivocal and transparent” account of what he knew and when.

Under parliamentary convention, knowingly misleading the House is treated as a serious matter that can lead to resignation. The column noted that Mandelson had told a television interviewer on Monday that more embarrassing revelations about his relationship with Epstein were due to be published, and Hodges questioned whether Mr. Starmer had sought a detailed account from his ambassador before making his public declarations of confidence.

Downing Street has previously said appointments follow full due process. Mr. Starmer’s office did not immediately respond to the Daily Mail column’s demands for further explanation and an assessment of the newly reported material. Mandelson has also made public statements in recent days expressing regret for his association with Epstein, according to the column.

The allegations draw new scrutiny to longstanding questions about how political appointments are vetted and how information about officials’ past associations is handled when it concerns sensitive diplomatic relationships. Hodges framed his column as an “acid test” of the prime minister’s pledge on standards and called for transparency over the files and communications that informed Mandelson’s appointment.

The story is developing, and further responses from Downing Street, the Cabinet Office and Mandelson may clarify the provenance of the reported documents and the timeline of what Mr. Starmer and his advisers were told.