Labour says the internal government paper, marked “official sensitive”, warns of new customs checks between Great Britain and Northern Ireland – which the government has claimed would not exist.
Speaking in central London on Friday Mr Corbyn told journalists: “Today I can reveal further hard evidence that Johnson is deliberately misleading the people”.
Download the new Indpendent Premium app
Sharing the full story, not just the headlines
He added: “This document is very ominous. There will be other secret reports like this one in every government department that reveal the disastrous impacts of his policies on the safety of the food you eat, on the rights you have at work, on the pollution of the air that we breathe and on the jobs and industries that people work in. These reports exist but the government is hiding them from you because in this election the Conservatives want you to vote blind.”
The leaked document is marked “official sensitive” and appears to originate from the Treasury. It is titled “Unfettered access to the UK internal market” and appears to be an official analysis of the so-called “Northern Ireland protocol” which replaces the backstop negotiated by Theresa May.
The Labour leader said the document was “fifteen pages that paint a damning picture” of the Brexit deal. He said that page five of the document stated: “There will be customs declarations and security checks between Northern Ireland and Great Britain” – which Mr Johnson has repeatedly denied in public.
Mr Corbyn added: “It is there in black and white. It says there will be customs declarations, absolutely clearly, for trade going from Northern Ireland to Great Britain.
“The Government cannot rule out regulatory checks, rules of origin checks and animal and public health checks also. For trade going the other way, from Great Britain to Northern Ireland, there will be all of the above plus potentially damaging tariffs.”
The leaked document seems to confirm in the government’s own words what essentially all trade experts say about the Brexit deal with regard to customs, but which Mr Johnson has continued to deny point-blank when asked in public.
At the start of the election campaign, the prime minister was asked in person by Northern Ireland business leaders whether they would be subject to customs declarations.
“You will absolutely not,” he told them. “If anyone asks you to do that tell them to ring up the Prime Minister and I’ll direct them to put that for in the bin.”
Earlier in the campaign Labour presented separate leaked documents that showed UK negotiators have been repeatedly discussing the National Health Service with US trade officials, despite claims by Boris Johnson that the NHS is not “on the table” in talks.