The government is preparing for food and medicine shortages, delays to cross-border trade and public disorder under a no-deal Brexit, according to documents released following a demand by MPs.
A five-page dossier on the government’s "reasonable worst case planning assumptions" was published after the government was defeated in a vote on the final day before parliament was prorogued.
The document, prepared as part of ‘Operation Yellowhammer’, says the flow of cross-Channel goods could be reduced to 40% of current rates on day one, with "significant disruption lasting up to six months."
"Unmitigated, this will have an impact on the supply of medicines and medical supplies," it says.
"The reliance of medicines and medical products' supply chains on the short straits crossing make them particularly vulnerable to severe extended delays."
However, it will "not be practical to stockpile products to cover expected delays of up to six months" and warns that "any disruption to reduce, delay or stop the supply of medicines for UK veterinary use would reduce our ability to prevent and control disease outbreaks, with potential detrimental impacts for animal health and welfare, the environment and wider food safety."
On food, it warns that some fresh supplies will decrease and that "critical dependencies for the food chain" such as key ingredients "may be in shorter supply."
It says these factors would not lead to overall food shortages "but will reduce the availability and choice of products and will increase price, which could impact vulnerable groups".
The document also says that “low-income groups will be disproportionately affected by any price rises in food and fuel."
And it warns that “protests and counter-protests will take place across the UK and may absorb significant amounts of police resource. There may also be a rise in public disorder and community tensions."
The risk to water supplies is low, it says, with water companies "well prepared for any disruption".
On trade, the document says France will impose EU mandatory controls on UK goods from day one, and that “in a reasonable worst-case scenario, HGVs could face maximum delays of 1.5-2.5 days before being able to cross the border”.
It adds that “the worst disruption to the short Channel Straits might last for up to 3 months before it improves by a significant level to around 50-70% (due to more traders getting prepared), although there could continue to be some disruption for significantly longer”.
UK citizens travelling to and from the EU "may be subject to increased immigration checks at EU border posts".
The government also warns of tensions at sea, with up to 100 foreign fishing boats expected to illegally enter Scottish waters alone, with more around the rest of the UK.