A secret Whitehall dossier warning of the impact of a no-deal Brexit has been dismissed by a minister as "scaremongering" as the Government sought to play down the documents.

The Sunday Times reports that there will be food and fuel shortages, and a hard border with Ireland in the event of No Deal.

Prime Minister Boris Johnson has repeatedly said he intends for the UK to leave the EU on October 31.

Kwasi Kwarteng said a "lot of people" were playing into "Project Fear" following the leak of documents on the Government's Operation Yellowhammer, which detailed the "most likely aftershocks" of the UK crashing out of the EU.

However, Michael Gove - the Cabinet minister responsible for no-deal planning - insisted Yellowhammer represented a "worst-case scenario", and a Downing Street source claimed it had been leaked by a former minister.

Published by the Sunday Times, the documents warn that Britain will be hit with a three-month "meltdown" at its ports, a hard Irish border and shortages of food and medicine if it leaves without a deal.

A senior Whitehall source told the paper: "This is not Project Fear - this is the most realistic assessment of what the public face with no deal. These are likely, basic, reasonable scenarios - not the worst case."

According to the documents, petrol import tariffs would "inadvertently" lead to the closure of two oil refineries, while protests across the UK could "require significant amounts of police resources" in a no-deal scenario.

They also warn that Gibraltar could face delays of up to four hours at the border with Spain for "at least a few months".

But when asked about the dossier, Business Minister Mr Kwarteng told Sky's Sophy Ridge on Sunday: "I think there is a lot of scaremongering around and a lot of people are playing into Project Fear and all the rest of it.

"We've got to prepare for no-deal. In fact the previous prime minister created DExEU and she said that the mandate of DExEU last year, last summer, was to prepare for no-deal...

"Now we've got a new Prime Minister who is very much focused on that and the scale and intensity of those preparations are increasing and we will be fully prepared to leave without a deal on October 31."

Chancellor of the Duchy of Lancaster Mr Gove tweeted: "We don't normally comment on leaks - but a few facts - Yellowhammer is a worst case scenario - v significant steps have been taken in the last 3 weeks to accelerate Brexit planning - and Black Swan is not an HMG doc but a film about a ballet dancer..."

A Number 10 source said: "This document is from when ministers were blocking what needed to be done to get ready to leave and the funds were not available. It has been deliberately leaked by a former minister in an attempt to influence discussions with EU leaders.

"Those obstructing preparation are no longer in Government, £2 billion of extra funding already made available and Whitehall has been stood up to actually do the work through the daily ministerial meetings. The entire posture of Government has changed."

The Government of Gibraltar said the Operation Yellowhammer documents were "out of date" and based on "planning for worst case scenarios".

Fabian Picardo, the chief minister of Gibraltar, said: "We do not want a no-deal Brexit. We think it is bad for Gibraltar. We are, nonetheless, now ready for it. The matters raised in the outdated Yellowhammer leak have already been responsibly addressed in detail."

Meanwhile, Tory former cabinet ministers Iain Duncan Smith and Owen Paterson claimed the leak was an example of the "establishment" plot to "sow fear in people's minds".

In a joint statement, they said: "This Operation Yellowhammer leak is the version of what the contingency executive put together. We remember attending a briefing on privy council terms which they said was not worst case but reasonable worst case. Theresa May had asked for this to be done. It was obviously Project Fear dressed up.

"For example, on the delays at the port we asked if they had discussed their expectation with the port authorities of Calais/Pas du Nord who had already said that there would be no extra delays at Calais and they said, (after a great deal of shuffling of feet) 'no'.

"We asked why not and they said they had not been asked to do so. There were other areas where it was clear they had not been asked to get balance but instead dress up previous versions of other worst-case scenarios.

"The whole thing was an attempt to frighten us and didn't stand up to scrutiny. We have never seen officials look so uneasy under questioning.

"The fact that this document was 'found' in a Westminster pub tells you all you need to know about this continuing establishment plot to sow fear in people's minds. This is an abuse of the proper use of the Civil Service and must be stopped."

However, the SNP's Stephen Gethins said the documents lay bare the "sheer havoc Scotland and the UK are hurtling towards".

"The Tory Prime Minister is in a state of delusion and denial over the impact his extreme Brexit plans will have on essential supplies such as food, medicines and fuel," he said.

"The worrying reality is that these internal Government papers are only setting out the best-case scenario. It is clear that even in the face of disaster this Tory Government simply plans to walk over the cliff-edge, dragging Scotland with it."