Documents from the Government's Operation Yellowhammer no-deal Brexit preparations have been released.
The files outline the "reasonable worst case planning assumptions" in the event of the UK crashing out of the EU without an agreement.
MPs had voted for a motion to order the publication of the Yellowhammer documents, which warn of delays lasting three months at Channel crossings.
While the no deal plans were published ahead of the Wednesday evening deadline agreed in the Commons, the Government said it was refusing to release internal memos about the prorogation of Parliament.
The Government said the request was "unprecedented, inappropriate and disproportionate."
Former attorney general Dominic Grieve's demand for all written and electronic contact about the temporary suspension of Parliament and Operation Yellowhammer documents since July 23 to be released was approved by MPs by 311 votes to 302 on Monday.
His motion asked for all correspondence and communications, formal or informal, including WhatsApp, Telegram, Signal, Facebook Messenger, private email accounts, text messages, iMessage and official and personal mobile phones connected to the present Government since July 23 relating to prorogation.
According to the files, low-income groups will be disproportionately affected by any prise rises in fuel and food, as well as increased immigration checks at EU borders.
It also states: "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 document also says: "Low-income groups will be disproportionately affected by any price rises in food and fuel."
UK citizens travelling to and from the EU "may be subject to increased immigration checks at EU border posts," it also states.
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It warns: "This may lead to passenger delays at St Pancras, Cheriton (Channel Tunnel) and Dover where juxtaposed controls are in place.
"Dependent on the plans EU member states put in place to cope with these increased immigration checks, it is likely that delays will occur for UK arrivals and departures at EU airports and ports.
"This could cause some disruption on transport services. Travellers may decide to use alternative routes to complete their journey."
The document 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."
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"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, they 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 risk to water supplies is low, it says, with water companies "well prepared for any disruption".