0146 GMT February 18, 2020
The report also outlined that trade will be severely disrupted, with the agri-food sector hit the hardest, according to independent.ie.
The UK is heading towards a constitutional crisis at home and a showdown with the EU as British Prime Minister Boris Johnson has repeatedly vowed to leave the bloc on October 31 without a deal unless it agrees to renegotiate the Brexit divorce.
The Sunday Times said the forecasts compiled by the Cabinet Office set out the most likely aftershocks of a no-deal Brexit rather than the worst case scenarios.
"Compiled this month by the Cabinet Office under the codename Operation Yellowhammer, the dossier offers a rare glimpse into the covert planning being carried out by the government to avert a catastrophic collapse in the nation's infrastructure," the Times reported.
The report outlines the fall-out that Britain crashing out of the EU without a deal would cause to Northern Ireland.
It says: "On day one of no deal, her Majesty's government will activate the 'no new checks with limited expectations' model on March 13, establishing a legislative framework and essential operations and system on the ground, to avoid an immediate risk of a return to a hard border on the UK side.
"The model is likely to prove unsustainable because of economic, legal and biosecurity risks."
It notes that EU tariffs on goods entering Ireland ‘will severely disrupt trade’, forcing some businesses to close or relocate.
"The agri-food sector will be hardest hit, given its reliance on complicated cross-border supply chains and the high tariff and non-tariff barriers to trade.
"Disruption to key sectors and job losses are likely to result in protests and direct action with road blockades.
"Price and other differentials are likely to lead to the growth of the illegitimate economy.
"This will be particularly severe in border communities where criminal and dissident groups already operate with greater freedom," the document warns.
Meanwhile, they said up to 85 percent of lorries using the main English channel crossings ‘may not be ready’ for French customs, meaning disruption at ports would potentially last up to three months before the flow of traffic improves.
"The file, marked ‘official-sensitive’ — requiring security clearance on a ‘need to know’ basis — is remarkable because it gives the most comprehensive assessment of the UK’s readiness for a no-deal Brexit."
After more than three years of Brexit dominating EU affairs, the bloc has repeatedly refused to reopen the Withdrawal Agreement which includes an Irish border insurance policy that Johnson's predecessor, Theresa May, agreed in November.
Johnson will this week tell French President Emmanuel Macron and German Chancellor Angela Merkel that the Westminster Parliament cannot stop Brexit and a new deal must be agreed if Britain is to avoid leaving the EU without one.
The British prime minister is coming under pressure from politicians across the political spectrum to prevent a disorderly departure, with opposition leader Jeremy Corbyn vowing this week to bring down Johnson's government in early September to delay Brexit.
It is, however, unclear if lawmakers have the unity or power to use the British Parliament to prevent a no-deal departure — likely to be the United Kingdom's most significant move since World War II.
Opponents of no deal say it would be a disaster for what was once one of the West's most stable democracies. A disorderly divorce, they say, would hurt global growth, send shockwaves through financial markets and weaken London’s claim to be the world’s preeminent financial center.
Brexit supporters say there may be short-term disruption from a no-deal exit but that the economy will thrive if cut free from what they cast as a doomed experiment in integration that has led to Europe falling behind China and the US.