Personal text messages between Lord Mandelson, Sir Keir Starmer and the Prime Minister's Chief Secretary Darren Jones may have been withheld from Parliament, sources familiar with the matter have told GB News.
It is claimed that some personal phone messages sent to Lord Mandelson from both Sir Keir and Mr Jones were not included in today's damning dossier.
Meanwhile, Lord Mandelson himself is apparently not prepared to release anything after the New Labour grandee received legal advice not to do so while Scotland Yard's criminal investigation remains ongoing.
However, the claim was denied by Downing Street sources.
"Nothing is being withheld on the messages," one No10 insider told GB News.
A No10 spokesman added: "In the same way as other ministers, the PM has fully complied with the Humble Address by providing all the information he holds as required."
"The information submitted has been published by the Cabinet Office."
Mr Jones also offered an alternative explanation as to why his messages were not included in the 598-page report.
Lord Mandelson's messages with Sir Keir Starmer have been 'withheld', sources tell GB News
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The Prime Minister's Chief Secretary said that his messages to Lord Mandelson had not been included because he had been using the disappearing messages function on WhatsApp.
He told MPs: “I do recall having some limited exchanges with Peter Mandelson over WhatsApp, including those I’ve already discussed in the media.
"But these conversations did not involve transacting Government business, and were in line with official guidance on the use of non-corporate communications channels at the time.”
It is understood that Lord Mandelson has virtually no messages on his personal mobile phone.
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Darren Jones addressed the release of new documents in the Mandelson files
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Everything was said to have been conducted on his official phone during his short-lived stint as the UK's Ambassador to the US.
However, the decision not to include messages from the Prime Minister sparked concern from Labour's political rivals.
Reform UK chief whip Lee Anderson told GB News: "The Prime Minister may have serious questions to answer, but until we see the files, we will never know.
"This stinks of a cover-up, and the public will not forgive Labour."
Alex Burghart has hit out at the Labour Government following the release of the second batch of Peter Mandelson files | PARLIAMENT TVShadow Chancellor of the Duchy of Lancaster, Alex Burghart, responded directly to Mr Jones's remarks in the House of Commons.
He said: “Some ministers have duly handed over their WhatsApp messages. It is clear that some have not.
"Are we to believe that there was no WhatsApp exchange at all between the Prime Minister and Peter Mandelson?
"We know that there were, because it’s been reported in the press, and yet those messages reported in the press do not appear in the release today.
Lord Mandelson will not return to the House of Lords | GETTY“It is clear that some messages have gone missing.”
Mr Jones replied: “This tranche, plus the first tranche of documents, represent the entirety of the documents that the Government has for disclosure, except for those that have been made available to the Metropolitan Police.”
Tory sources have also told GB News that Mr Jones's remarks did not centre around Lord Mandelson's refusal to hand over his private home.
Cabinet Office Minister Nick Thomas-Symonds's early messages with Lord Mandelson were not available following a second phone theft in October 2025.
Morgan McSweeney, who served as Sir Keir's chief of staff from October 2024 to February 2026, also had his personal device snatched during a late-night incident just days later.