The UK's top civil servant has warned the powers of the Northern Ireland secretary of state are insufficient to deal with the "controversy" that would surround decisions needed to be taken in the event of a no-deal Brexit and full-scale direct rule from London would be necessary.
The warning comes in a letter leaked to the Daily Mail, in which it was also warned there would be hikes in food prices, a recession worse than the crash of 2008 and pressures on law enforcement.
The paper says the letter was sent to every member of the Cabinet by Sir Mark Sedwill. It's reported they had asked for the assessment from Sir Mark - who is Cabinet Secretary and also the National Security Adviser - to ensure they were "complying with their duty to govern in the national interest".
In it he expresses concerns Northern Ireland would face "more severe" consequences particularly with the lack of a devolved government.
He says direct rule would be required from London.
"The running of Northern Ireland under no deal is a sensitive issue," he said.
"The current powers granted to the Northern Irish Secretary would not be adequate for the peace, breadth or controversy of the decisions needed to be taken through a no deal exit. Therefore we would have to introduce direct rule."
He also warned the financial pressures facing the UK would mean a recession worse than the one created after the 2008 banking crash, he argues because it would be localised to the UK and not a global crisis.
Sir Mark goes on: "There would be enormous pressure on the Government to bail out companies on the brink."
He is not the first to raise the prospect of the government providing support when the UK leaves the EU. A a recent Northern Ireland Affairs Committee meeting the DUP MP Sammy Wilson said the government would mitigate for the negative impacts of Brexit.
Theresa May is holding marathon cabinet sessions on Tuesday after Parliament again rejected options on Brexit alternatives. Unless the prime minister requests a delay to Brexit at an emergency summit of EU leaders on April 10, the UK leaves with no-deal two days later.
Downing Street declined to comment on Sir Mark's letter.