According to "Operation Yellowhammer", the secret dossier leaked to the Sunday Times, exposes the areas that could be most vulnerable if the country exits the European Union (EU) without a deal on October 31.
In response to the leak, Cabinet Minister Michael Gove, who is responsible for no-deal preparation, said on Sunday night that the document was old and Brexit planning had accelerated since Boris Johnson took over as the new Prime Minister last month.
Gove said some of the concerns about a no deal Brexit had been "exaggerated".
"It's certainly the case that there will be bumps in the road, some element of disruption in the event of no-deal.
"But the document that has appeared in the Sunday Times was an attempt, in the past, to work out what the very, very worst situation would be so that we could take steps to mitigate that.
"And we have taken steps," the BBC quoted Gove as saying.
The leak comes as Johnson is slated to meet European leaders French President Emmanuel Macron and German Chancellor Angela Merkel during his first trip abroad as Prime Minister later this week.
A Downing Street source told the BBC later on Sunday that the dossier had been leaked by a former Minister in an attempt to influence discussions with EU leaders.
The document "is from when ministers were blocking what needed to be done to get ready to leave and the funds were not available", the sources added.
( With inputs from IANS )