Former British chancellor Philip Hammond has demanded an official apology from Prime Minister Boris Johnson after Number 10 sought to blame disgruntled ministers for the leak of no-deal documents.
Mr Hammond said the Operation Yellowhammer document, which set out in stark terms the potential impact of a no-deal Brexit, was dated August 2019 - after Mr Johnson had taken office.
Mr Hammond wrote that according to the media, a Number 10 source had briefed the dossier was "deliberately leaked by a former minister in an attempt to influence discussions with EU leaders".
The documents, obtained by the Sunday Times, indicated the UK will be hit with a three-month "meltdown" at its ports, a hard Irish border and shortages of food and medicine after it leaves the EU without a deal.
Mr Hammond said: "The clear implication was that a minister in the last government has retained, and then leaked, a copy of this document. The media has speculated accordingly on the source of this document."
But the former chancellor added: "It has now become apparent that the leaked document was, in fact, dated August 2019 and would not, therefore, have been available to any former minister who is not serving in the current administration.
"Accordingly, I am writing on behalf of all former ministers in the last administration to ask you to withdraw these allegations which question our integrity, acknowledge that no former minister could have leaked this document, and apologise for the misleading briefing from No. 10."
A Downing Street source said: "I'm sure the Prime Minister will reply in due course.
"I'm sure he will be interested to learn that Philip Hammond represents all former ministers."
The source disputed the suggestion that it had been drawn up under Mr Johnson's premiership.
"Various briefings made clear that the Yellowhammer document was prepared for the previous administration and presented at the first meeting of the XO (Exit Operations committee) and knocked back by ministers at the time," said the source.
"It doesn't reflect the changes made by the government in terms of preparing for no-deal."