The government has published more than 1,000 pages of documents relating to Lord Mandelson's appointment as the UK's ambassador to the US.
The papers include messages between Lord Mandelson and ministers, exchanging advice and news - as well as criticism of the No 10 operation, Labour MPs and the prime minister himself.
On 2 May 2025, Lord Mandelson wrote to Pat McFadden (then a Cabinet Office minister, now the work and pensions secretary) saying: "Keir lacks verve as does the Cabinet as a whole."
Then in July that year, messages between the two appear to show Lord Mandelson criticising advisers in No 10, saying they are good but "they don't work as a team, they are not led and none of them really know what Keir thinks or wants.
"In fact most of them don't think Keir knows what he wants."
Later that month, in a further message to McFadden, Lord Mandelson says: "I have a feeling that Keir is now consistently going for direction B. His recanting on his immigration speech, on welfare, now Gaza.
"There is definitely a 'let Keir be Keir' trend. This is what Morgan [McSweeney] senses and so it is particularly acute for him. His view from when Keir first stood is that the cycle has been the same, advance/buckle/advance/buckle."
Lord Mandelson later adds: "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."
In the exchanges, McFadden also describes conversations he had with other Labour politicians about the welfare system and public spending in a pretty blunt way.
"Every meeting I have is 'who can we tax in order to pay benefits to others'," he wrote to Lord Mandelson. "They're asking the wrong questions".
Allies of McFadden point out that message was sent before he was in charge of the UK's benefits regime. He was running the Cabinet Office at the time.
A spokesperson for the work and pensions secretary said: "Pat has fully complied with the Humble Address and handed over all messages.
"His only contact with Peter Mandelson since he left government has been to urge him to think about the victims in all this and apologise to them."
Lord Mandelson and senior officials discussed commissioning an official government "red box" to give as a gift to US President Donald Trump.
Amid complications in organising this, the former US ambassador told No 10 chief of staff Morgan McSweeney he'd "gone tonto" and that the "saga" was "like something out of [TV comedy show the] Thick of It".
Sir Olly Robbins, then the top official at the foreign office, said "one of the gifts that would mean the most to the President would be a red dispatch box with the gold crest and lettering mimicking a UK Government Ministerial box but with 'President of the United States' inscribed upon it."
Business Secretary Peter Kyle said he would "action" advice from Lord Mandelson to include "more positive language about AI" at the start of a speech at a major international security conference.
On 8 February 2025, Lord Mandelson told Kyle, who was then the government's technology secretary, that his speech would "benefit from more positive language about AI up front before you get into the security stuff".
Kyle replied: " That's all v good advice which I'll action. Thank you."
Six days later Kyle gave a speech at the Munich Security Conference in which he said "in the UK, we reject the doomsayers and the pessimists" about artificial intelligence.
In 2024, before he was appointed ambassador, Lord Mandelson lobbied Oxford alumni among Labour ministers to vote for him to be the next chancellor of the university, including Emma Reynolds, Ed Miliband, Torsten Bell, Georgia Gould, Ellie Reeves, Kirsty McNeill and James Murray.
Lord Mandelson was beaten to the largely ceremonial role by William Hague, the former leader of the Conservative Party.
