A no-deal Brexit could lead to outbreaks of disease and shortages of medicine, fresh food and fuel, with the poorest hit worst, official government documents show.
The papers – marked “official sensitive” – also warn of “a rise in public disorder and community tensions”, “panic buying” at supermarkets, and huge traffic jams in Kent as the EU imposes tariffs and checks on UK goods.
There are also likely to be delays for passengers at airports and ports as British citizens will face more stringent immigration checks.
The Operation Yellowhammer “reasonable worst case scenario” papers are dated August 2, after Boris Johnson became prime minister, and were released after his administration lost a Commons vote on Monday demanding publication.
A separate request to publish communications between officials about the controversial shutdown of parliament was rejected by the government, which argued its publication would break several laws.
The papers could put huge pressure on the prime minister to abandon his pledge to quit the EU, deal or no-deal, on October 31 – a promise is already running contrary to a law passed by MPs to block no-deal on Halloween.
Michael Gove, the cabinet minister in charge of no deal planning, insisted the Yellowhammer documents were not “a prediction of what is most likely to happen”.
“It describes what could occur in a reasonable worst case scenario, thus providing a deliberately stretching context for government planning to ensure that we are prepared for exit,” he said.
But Sunday Times journalist Rosamund Urwin, who obtained a near-identical leak of Yellowhammer documents last month, insisted the version she had was a “base scenario”, suggesting it indicated what was likely to happen.
Much of the disruption will be the result of delays in goods crossing the Channel, with lorry flows cut to about 40-60% of current levels, resulting in traffic jams up to two-and-a-half days long as drivers wait to cross the border.
Delays through ports will lead to shortages of medicines and medical supplies, as three-quarters are imported across the Channel, making them “particularly vulnerable to severe extended delays”, the documents said.
Disruption to the supply of medicines for vets could also hamper Britain’s ability to prevent and control disease outbreaks, some of which will affect humans.
There could also be damage to animal health and welfare, the environment, food safety and availability.
The industry will not be able to stockpile as much medicine as it did when preparing for the previously planned exit day of March 29, when it stored around four to 12 weeks worth.
There will also be a shortage of certain types of fresh food as well as “critical” ingredients, chemicals and packaging for the food supply chain.
These two factors “will not cause an overall shortage of food in the UK but will reduce availability and choice of products and will increase price, which could impact vulnerable groups”.
Britain’s growing season will also have ended and the industry will be under more pressure due to preparations for Christmas.
“There is a risk that panic buying will cause or exacerbate food supply disruption,” the report says.
The report also warns of “a rise in public disorder and community tensions” with protests absorbing “significant amounts” of police resources.
And there will be fuel shortages in the south east of England due to traffic queues in Kent, particularly if they block the Dartford crossing.
It could take up to three months before the flow of trucks crossing the Channel improves to just 50-70% of current levels.
There will also be passenger delays at St Pancras, Dover and the Channel tunnel as UK citizens are subject to increased EU immigration checks.
Passengers travelling to and from EU airports and ports will also face delays due to more checks.
In the waters surrounding the UK there are likely to be clashes between fishing boats which incorrectly stray across sea borders.
And Northern Ireland businesses will face “severe” disruption, with some firms going bankrupt or relocating to avoid paying EU tariffs.
The agri-food sector will be hit hardest, with job losses potentially leading to protests and direct action, including road blockages.
Smuggling across the Irish border is likely to increase and disruption “will be particularly severe in border communities where both criminal and dissident groups already operate with greater threat and impunity”, the papers said.
Reacting to the documents, shadow Brexit secretary Keir Starmer said it was “completely irresponsible for the government to have tried to ignore these stark warnings and prevent the public from seeing the evidence.”
Labour’s home secretary Diane Abbott tweeted: “Disruption to crime data sharing and an overstretched police force left to deal with public unrest - the #Yellowhammer docs show just how much the Tories No Deal Brexit is putting our safety at risk.”
Meanwhile, Green Party MP Caroline Lucas said that it “simply beggars belief that any government could be willing to contemplate a future that will cause so much pain and disruption – much less rush towards it.
“Is this what Boris Johnson meant by ‘do or die’?”
In letters to Dominic Grieve and Hilary Benn, the MPs who led the push for publication, Gove meanwhile said the government could not comply with requests to release cabinet papers as it would breach the ministerial code and the Freedom of Information Act.
A section of the Yellowhammer documents were also redacted to protect commercial sensitivity.
Replying directly to Grieve, Gove also explained that the government could not fulfil a request to publish all communications relating to prorogation, including WhatsApp, Telegram, Signal, Facebook, email, text and iMessages sent to, from or between Johnson’s team of top Downing Street advisers.
Gove described that request as an “unprecedented, inappropriate, and disproportionate” use of parliament as the officials have no right of reply and obtaining the information would put the government in breach of several laws, including the Human Rights Act and Data Protection Act.