The United Kingdom is likely to face shortages of food, fuels and medicines if it abandons the block without a transition deal, according to estimates compiled by the Cabinet codenamed Operation Yellowhammer.
Medical supplies coming from Europe will be "vulnerable to serious long-term delays," and the availability of fresh food will be reduced, leading to higher prices, the newspaper reported.
He added that the public and business remain largely unprepared for a fruitless Brexit deal and that increasing "fatigue from leaving the EU" has hampered emergency planning.
"This is not project fear ̵
A Downling Street spokesman told CNN that "we will not comment on expired documents."  Some have questioned the accuracy of the report.The government of Gibraltar – which is the British territory on the southern coast of Spain – told CNN the briefings are "outdated" and based on planning for "worst case scenarios" they have already considered. "
Countdown to 31 October
The United Kingdom had to leave EU on March 29 this year. But he was given a new deadline by 31 October after failing to adopt a withdrawal agreement through Parliament.
This week Johnson will make his first trip abroad as prime minister, heading to Berlin and Paris, where analysts say he is expected to make a case for a new Brexit
He will meet with French President Emmanuel Macron and German Chancellor Angela Merkel before the G7 summit in Biarritz, France next weekend.
The prospect of a Brexit breakthrough seems unlikely. The EU has repeatedly said that the withdrawal agreement – which has been won three times in the British Parliament – is not ready for renegotiation.
Without going back
The leaked file comes as the British government on Sunday was missing a historic Brussels act of 1972 – effectively ending all EU law in the UK.
The repeal of the act will enter into force on 31 October, when the United Kingdom officially leaves the EU.
"This is a clear signal to the people of this country that there is no going back – we are leaving the EU, as promised on October 31, regardless of the circumstances," EU Secretary of State Steve Barclay said in a statement.
The Labor Party leader has announced that he will begin reviewing a no-confidence motion in the Johnson government at the earliest opportunity and will seek to form a "strictly time-bound" care government in a letter sent to leaders of other parties in Great Britain.
With the clock running on October 31, time is running out for a breakthrough in the Brexit impasse. CNN's Max Foster in London and Elizabeth Wells in Atlanta contributed to this report