Peter Mandelson’s appointment as Britain’s ambassador to the United States continues to cast a long shadow over Keir Starmer’s government, with a newly released tranche of official documents revealing sharp private criticism of both the prime minister and his Downing Street operation.More than 1,500 pages of correspondence, WhatsApp messages, letters and briefing papers have been published by the government following a Commons demand for transparency over Mandelson’s controversial appointment.Among the most damaging disclosures are Mandelson’s candid assessments of the prime minister, whom he said “lacks verve”, alongside criticisms of a No 10 operation he described as “beleaguered and bereft”. The papers also contain exchanges with senior ministers, discussions surrounding his appointment to Washington, and evidence of broader concerns about the direction of Starmer’s government.'Keir lacks verve’: Mandelson’s blunt verdict on StarmerThe most politically explosive revelations centre on Mandelson’s private conversations with Pat McFadden, one of Starmer’s closest allies.In a message sent on 2 May 2025, Mandelson wrote: “Keir lacks verve as does the Cabinet as a whole.” He also questioned the government’s strategic direction, asking: “The mantra is Plan for Change. But what is the Plan?”His criticism intensified in subsequent exchanges. Discussing Starmer’s team in Downing Street, Mandelson said advisers were capable individuals but “they don't work as a team, they are not led and none of them really know what Keir thinks or wants”.He added: “In fact most of them don't think Keir knows what he wants.”Later messages suggested Mandelson believed Starmer repeatedly retreated under pressure. Referring to disputes over immigration, welfare and Gaza policy, he wrote: “There is definitely a 'let Keir be Keir' trend.”Describing the prime minister’s leadership style, Mandelson said the pattern had become “advance/buckle/advance/buckle”.Following a visit to Downing Street in July 2025, he delivered perhaps his most scathing assessment, telling McFadden: “I went in to No 10 after I saw you. It is beleaguered and bereft. It requires complete revamp and infusion of purpose and confidence to get anywhere.”The messages also reveal frustrations among other senior Labour figures. McFadden complained that discussions with colleagues frequently focused on raising taxes to fund welfare spending, writing: “Every meeting I have is 'who can we tax in order to pay benefits to others'. They're asking the wrong questions.”'You will never regret it’: The ambassadorial appointment under scrutinyThe documents also shed fresh light on how Mandelson secured the Washington posting.In a handwritten note to then Foreign Secretary David Lammy in November 2024, shortly before his appointment was confirmed, Mandelson urged ministers to back his candidacy.“I just wanted you to know that if you were minded to appoint me I would make sure you never regret it,” he wrote.Acknowledging the challenge of managing relations with President Donald Trump’s administration, Mandelson added: “I fear that navigating Britain's interests through the Trump administration will require super-human skills and luck and a massive team effort.”The newly released files arrive against the backdrop of continuing controversy over the appointment. Earlier disclosures revealed officials had warned of potential “reputational risk” linked to Mandelson’s friendship with convicted sex offender Jeffrey Epstein, while other documents showed concerns over aspects of his background and business connections.The latest release also notes that Mandelson declined a government request to provide material from his personal phone during the document-gathering process.