Food, fuel and medicine shortages will quickly follow a no-deal Brexit which will trigger three months of border chaos, leaked government documents admit.

The dossier also warns that new border checks would be needed in Ireland – contradicting repeated denials that the red line, risking the return of terrorism, would be crossed.

The Cabinet Office even warns of the risk of a “failure” in chemical supplies, undermining Boris Johnson’s boast that “there will be clean drinking water, whatever the deal we do”.

Significantly, the documents set out the most likely consequences of a crash-out Brexit on 31 October, rather than worst-case scenarios.

Border delays could “affect fuel distribution”, with delays of up to two and a half days for lorries and significant disruption lasting up to three months.

Medical supplies will “be vulnerable to severe extended delays” as three-quarters of the UK’s medicines enter the country via the main Channel crossings.

Tariffs in the event of a no-deal Brexit Show all 15 1 /15 Tariffs in the event of a no-deal Brexit Tariffs in the event of a no-deal Brexit Pork There will be tariffs on pork in order to protect British farmers Getty Tariffs in the event of a no-deal Brexit Cheese There will be tariffs in place on some cheeses including €22.10/100kg of cheddar, €19.10/100kg of processed cheese and €18.60/100kg on some blue cheeses Getty Tariffs in the event of a no-deal Brexit Milk There will be no tariffs in place on milk Getty Tariffs in the event of a no-deal Brexit Car Parts There will be no tariffs on car parts imported from Europe PA Tariffs in the event of a no-deal Brexit Cars However finished cars will face tariffs of 10.6% Getty Tariffs in the event of a no-deal Brexit Alcoholic drinks There will be no tariffs on alcoholic drinks - except on some rums due to ingredients used in their distilling process Getty Tariffs in the event of a no-deal Brexit Beef There will be tariffs on beef in order to protect British farmers Getty Tariffs in the event of a no-deal Brexit Fish There will be no tariffs on many types of fish including cod, haddock, salmon and sea bass Getty Tariffs in the event of a no-deal Brexit Fruit and vegetables There will be no tariffs on almost all fruit and vegetables Getty Tariffs in the event of a no-deal Brexit Chocolate There will be no tariffs on chocolate or other cocoa products Getty Tariffs in the event of a no-deal Brexit Poultry There will be tariffs on poultry in order to protect British farmers Getty Tariffs in the event of a no-deal Brexit Ceramics There will be some tariffs in place on ceramis Getty Tariffs in the event of a no-deal Brexit Steel There will be no tariffs on steel Getty Tariffs in the event of a no-deal Brexit Coal There will be no tariffs on coal Getty Tariffs in the event of a no-deal Brexit Lamb/Mutton There will be tariffs on the meat of sheep in order to protect British farmers Getty

The Liberal Democrats said the documents, leaked to The Sunday Times, revealed that a no-deal Brexit had “wartime implications, in peacetime, all of them self-inflicted”.

“People will be horrified that Boris Johnson and the Conservatives are willing to pursue a plan that will lead to shortages of medicines, food and fuel,” said Tom Brake, the party’s Brexit spokesman.

The Operation Yellowhammer file warns that efforts to avoid the return of a hard border in Ireland are likely to prove “unsustainable”, with “significant economic, legal and biosecurity risks” that would require checks.

“Disruption to key sectors and job losses are likely to result in protests and direct action with road blockages,” it concludes.

Other official warnings include:

* Up to 85 per cent of lorries using the main Channel crossings “may not be ready” for French customs – with flows only at 50-70 per cent of the current rate even after three months.

* The closure of oil refineries, with 2,000 job losses, widespread strike action and disruptions to fuel availability.

* Passenger delays at EU airports, as well as at Eurotunnel services from London’s St Pancras station and at Dover.

* The availability of fresh food will be reduced and prices will rise. This could hit “vulnerable groups”.

* Potential clashes between UK and European Economic Area fishing vessels amid predictions that 282 ships will sail in British waters illegally on Brexit day.

* Protests across the UK, which may “require significant amounts of police resource[s]”.

* Rising costs will hit social care, with “smaller providers impacted within 2-3 months and larger providers 4-6 months after exit”.

A senior Whitehall source told The Sunday Times: “This is the most realistic assessment of what the public face with no deal. These are likely, basic, reasonable scenarios – not the worst case.”

However, despite the fact they are official documents, Kwasi Kwarteng, the energy minister, said: “There is a lot of scaremongering around. A lot of people are playing into project fear.”