Having been ordered to reveal the details by MPs, the five pages published on the government website warn of a rise in public disorder, delays lasting three months at Channel crossings, “significant” electricity price rises and impacts on medicine and food supplies.
The documents have been released after opposition MPs defeated the government in the House of Commons on Monday to order their publication.
Opposition MPs had also demanded the release of private messages between key Downing Street aides – including on WhatsApp and Facebook – over Boris Johnson’s five-week suspension of parliament.
The government has refused this request, describing it as “inappropriate”.
The “reasonable worst case planning assumptions” of Operation Yellowhammer detail:
- The worst disruption at Channel crossings might last for up to three months before improving
- Lorries could face maximum delays of two-and-a-half days before being able to cross the UK border
- Possible immigration delays for UK holidaymakers at the Channel Tunnel, ferry crossings and airports
- A likelihood of “significant” electricity price rises in Northern Ireland
- Medicine supplies will be “particularly vulnerable to severe extended delays”
- A potential reduction in the UK’s ability to prevent animal disease outbreaks due to reduced supplies of veterinary medicines
- Supplies of some fresh food will decrease, while supermarket prices may also rise
- Panic buying could increase food supply problems
- The possibility of urgent action to ensure access to clean water if there is a failure in the supply of chemicals – although the likelihood of this is considered “low”
- Disruption in law enforcement data sharing between the UK and EU
- Concerns that Gibraltar has not prepared well enough for a no-deal Brexit
- “Significant amounts” of police time being taken up by protests and a possible rise in public disorder
- The risk of disruption to fuel supplies in the South East of England
- Possible clashes between UK and EU fishing vessels
- UK efforts to avoid a hard border between Northern Ireland and the Republic of Ireland are “likely to prove unsustainable”
The document also warns the readiness for a no-deal Brexit among the public and businesses will “remain at a low level and will decrease to lower levels” due to uncertainty over the nature of the UK’s exit from the EU.
This readiness will be “further limited” by what the document describes as “increasing EU exit fatigue”.
The timing of a possible no-deal Brexit on 31 October also coincides with seasonal risks such as severe weather, flooding and flu outbreaks.
This could exacerbate a number of impacts of a no-deal Brexit and stretch resources, the document adds.
The end of the UK growing season and preparations for Christmas could also increase pressure on food supplies.
One paragraph of the document has been redacted due to “commercial sensitivity”, the government said.
Some of the Operation Yellowhammer details had already been leaked to The Sunday Times earlier this month, while opposition MPs questioned whether the government had released the full documents.
Following the publication of the papers on Wednesday night, Michael Gove – the Chancellor of the Duchy of Lancaster and the government minister in charge of no-deal planning – said: “The document is neither an impact assessment, nor 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.”
Labour shadow Brexit secretary Sir Keir Starmer said the documents “confirm the severe risks of a no-deal Brexit”.
He added: “It is completely irresponsible for the government to have tried to ignore these stark warnings and prevent the public from seeing the evidence.
“Boris Johnson must now admit that he has been dishonest with the British people about the consequence of a no-deal Brexit.
“It is also now more important than ever that parliament is recalled and has the opportunity to scrutinise these documents and take all steps necessary to stop no-deal.”
Former justice secretary David Gauke, who served in Theresa May’s government, said: “If anyone wondered why so many ministers in the last government are strongly opposed to a no-deal Brexit, read the Yellowhammer documents.
“But the problems with no deal don’t end with the short-term disruption. It’s in the long-term when the real damage will be done.”
His fellow former Conservative minister Phillip Lee, who is now a Liberal Democrat MP, described the Operation Yellowhammer details as “remarkable” and “explosive”.
He also questioned whether it was the full document, telling Sky News: “There’s obviously more to see.
“If you look at the details of this document, it is shocking.
“Really, did people vote in 2016 to have problems accessing clean water? Did they vote to have problems accessing necessary emergency medicines?
“Did they vote to have to have problems with access to fresh food? Of course they didn’t.”
:: Analysis: These five pages serve as a stark warning about the potential fallout from a no-deal Brexit
by Sam Coates, deputy political editor
When Boris Johnson came into Downing Street he said there would be bumps in the road if there is a no-deal Brexit.
In the last 10 days he has been having conversations with Conservative MPs.
I’ve spoken to two Tory MPs who were speaking to Mr Johnson in the context of the rebellion that took place last week that saw 21 other Tories chucked out.
They said he talked to them both about how he wanted a deal, and then he started talking about no-deal using language that they both said they hadn’t heard before.
He said that while individual problems could be mitigated for no-deal, he was aware of the enormous challenge that came with all of these potential problems all at once.
And that was an issue that frankly he didn’t want to see arise.
The political context of this conversation was that he was trying to convince these two Tory MPs he was sincere about getting a deal, something that they had not been sure that he was.
And he was trying to convince them that he was more on their side than perhaps his public positioning might suggest.
But you could just take what the prime minister appears to have said at face value – that all put together, these challenges are pretty eye-watering and not even necessarily political sustainable.
From the last 30 years of British political history, any one of the potential outcomes outlined in the document would be a national emergency and a crisis on an epic scale.
In 2001 we saw a lorry strike cause restricted access to fuel at the petrol pumps, and Tony Blair decided to delay a general election until it was sorted.
That’s the sort of consequence that you might see if there is a no-deal Brexit because of disruption at the border.
This five-page document outlines lots and lots of those challenges.
These stark warnings tonight from officials from Theresa May’s government in August suggest that the checklist of things the government would need to sort out is enormous.