Sir Keir Starmer resigned as UK Prime Minister and leader of the Labour Party on June 23, 2026, following a prolonged political crisis triggered by the appointment and subsequent dismissal of Peter Mandelson as ambassador to the United States. His resignation makes him the sixth UK prime minister to leave office within a decade since the 2016 Brexit referendum.
The Mandelson Appointment and Vetting Controversy
Appointment and Initial Vetting Failure
Peter Mandelson, a former Labour cabinet minister and European Union trade chief, was appointed UK ambassador to the United States by Prime Minister Starmer in December 2024. He took up the role in February 2025.
On January 28, 2025, UK Security Vetting, the government's vetting agency, denied Mandelson security clearance. The agency considered Mandelson a "borderline case" and was leaning toward recommending against granting him clearance for the ambassador role. The specific reasons for the vetting agency's concerns have not been publicly disclosed, though officials have stated they were not related to Mandelson's connections with Jeffrey Epstein.
Two days after the formal rejection, officials in the Foreign, Commonwealth and Development Office used a rarely exercised authority to override the vetting recommendation and grant Mandelson "developed vetting" clearance. The decision was made by Foreign Office officials. Prime Minister Starmer and other government ministers stated they were not informed of the initial denial or the override until March 2026.
Dismissal and Subsequent Revelations
Mandelson was removed from his ambassadorial position in September 2025, nine months after his appointment. The dismissal occurred after documents released by the US Department of Justice revealed new details about his relationship with Jeffrey Epstein, a convicted sex offender who died in prison in 2019.
In January 2026, the US Department of Justice released additional files including emails suggesting Mandelson passed sensitive government information to Epstein in 2009, while serving as Business Secretary during the 2008 financial crisis. The files also indicated that Epstein made payments totaling $75,000 to accounts linked to Mandelson between 2003 and 2004, and transferred £10,000 to Mandelson's partner in 2009. Mandelson has stated he does not recall receiving these payments.
Police Investigation and Arrest
London's Metropolitan Police initiated a criminal investigation into Mandelson for alleged misconduct in public office. Mandelson was arrested in February 2026 on suspicion of passing sensitive government information to Epstein. He was questioned and later released on bail pending further investigation. Police subsequently searched properties linked to Mandelson in London and Wiltshire.
Mandelson has consistently denied wrongdoing. He resigned from the House of Lords in February 2026 and from the Labour Party, stating he wished to avoid causing further embarrassment.
Government Documents and Parliamentary Inquiries
The UK government released multiple tranches of documents related to Mandelson's appointment, totaling over 1,500 pages. These included:
- A note from Mandelson to then-Foreign Secretary David Lammy stating the government would "never regret" his appointment
- Private WhatsApp messages in which Mandelson criticized Starmer's leadership, describing the government as "beleaguered and bereft" and stating Starmer "lacks verve"
- A vetting report confirming that Mandelson's relationship with Epstein continued after Epstein's 2008 conviction, with Mandelson staying at Epstein's residence in June 2009
"There was an 'atmosphere of pressure' from Downing Street to expedite Mandelson's appointment and a 'generally dismissive attitude' toward his security vetting clearance."
— Sir Olly Robbins, former top Foreign Office official, in testimony to the House of Commons Foreign Affairs Committee
Sir Olly Robbins, the most senior official at the Foreign Office, was dismissed after Starmer stated he lost confidence in him following the vetting controversy. A background report prepared before the appointment flagged potential business links to Russia and China as a concern. Jonathan Powell, national security adviser, described the appointment process as "weirdly rushed" in a September 2025 call summary.
Political Fallout and Leadership Crisis
Internal Party Dissent
Following the revelations about Mandelson's vetting and his relationship with Epstein, over 70 Labour MPs publicly called for Starmer's resignation. Six ministerial aides resigned from their positions.
Labour MP Jonathan Brash became the first government MP to publicly call for Starmer's resignation in April 2026, stating the party was "completely consumed by this scandal."
MP Catherine West announced a formal leadership challenge in May 2026, setting a deadline for Starmer's departure. She later withdrew her own challenge but continued collecting names of MPs who had lost confidence in the prime minister.
Key Staff Resignations
Morgan McSweeney, Starmer's chief of staff and a key architect of Labour's 2024 election victory, resigned in March 2026, taking responsibility for advising Starmer to appoint Mandelson. In his resignation statement, McSweeney said: "The decision to appoint Peter Mandelson was wrong. He has damaged our party, our country and trust in politics itself."
Tim Allan, Starmer's director of communications, also resigned.
Scottish Labour Leader Calls for Resignation
Anas Sarwar, leader of the Scottish Labour Party, became the most senior Labour figure to call for Starmer's resignation. Sarwar stated that the Westminster government's handling of the Mandelson controversy risked undermining Labour's prospects in the upcoming Scottish parliamentary elections scheduled for May 2026.
Local Election Losses
Labour suffered significant losses in local and regional elections held on May 1, 2026. The party lost 20% of its vote share, lost control of the Welsh Parliament for the first time, and failed to gain ground against the Scottish National Party in Scotland. The right-wing Reform UK party and the Green Party made gains at Labour's expense.
Cabinet Support and Opposition
Several cabinet members, including Deputy Prime Minister David Lammy, Home Secretary Shabana Mahmood, and Energy Secretary Ed Miliband, publicly expressed support for Starmer's continued leadership. However, reports indicated that three cabinet ministers—Lammy, Mahmood, and Foreign Secretary Yvette Cooper—had asked Starmer to set out a resignation plan.
Conservative Party leader Kemi Badenoch called for Starmer's resignation, stating he had "misled Parliament over Mandelson, misled the country and is taking the public for fools."
Resignation and Succession
Announcement
Starmer announced his resignation on June 23, 2026, stating that nominations for a successor would open the following month. He stated he would not "walk away" from his responsibilities but acknowledged that a leadership contest was necessary.
Potential Successors
Several figures were mentioned as potential candidates to succeed Starmer:
- Andy Burnham, Mayor of Greater Manchester, who won a by-election for the Makerfield parliamentary seat in June 2026. Burnham is considered a leading candidate and would become the seventh UK prime minister since the 2016 Brexit referendum if chosen.
- Wes Streeting, former Health Secretary, who resigned from the cabinet and announced his intention to stand in any leadership contest. Streeting called for a "proper contest" and criticized Starmer for failing to "meet the moment."
- Angela Rayner, former Deputy Prime Minister, who indicated she was ready to participate in a leadership contest. Rayner had previously resigned from the cabinet following scrutiny over her tax returns.
- Ed Miliband, Energy Secretary and former Labour leader.
Leadership Contest Rules
Under Labour Party rules, a leadership challenge requires nominations from at least 20% of Labour MPs (81 of 403 members). The contest involves party members and representatives from affiliated organizations such as trade unions.
Economic and Political Context
Brexit Anniversary and Economic Impact
Starmer's resignation coincided with the 10th anniversary of the June 23, 2016 referendum in which the UK voted 52% to 48% to leave the European Union. Since the referendum, the UK has had six prime ministers: David Cameron, Theresa May, Boris Johnson, Liz Truss, Rishi Sunak, and Keir Starmer. Starmer's successor would become the seventh.
Economic analyses have concluded that Brexit has reduced UK GDP by an estimated 6-8%, with business investment falling 12-13% and productivity declining 3-4%. Public opinion polls indicate that 52% of UK residents would now support rejoining the EU.
Government Borrowing Costs
During the leadership crisis, UK 10-year government bond yields rose to 5.07%, increasing government borrowing costs. Public sector net debt reached approximately £2.8 trillion, representing 94% of GDP.
Peter Mandelson's Apology and Current Status
In January 2026, Mandelson issued an apology to the victims of Jeffrey Epstein, stating: "I want to apologise to those women for a system that refused to hear their voices and did not give them the protection they were entitled to expect." He stated he would only apologize for his own ties if he had been aware of Epstein's actions or had been complicit.
As of his resignation from the House of Lords, Mandelson remains under police investigation. He has not been charged with any criminal offense.