Jeremy Corbyn has today published a new government report which he claims shows the "cold hard evidence" of the harm of Boris Johnson's Brexit.
Labour's leader held the document aloft at a press conference today in the second such bombshell leak of a confidential document in two weeks.
The first was a cache of nearly 500 pages which detailed trade talks between the US and UK.
Today's "very ominous" document was about trade arrangements between Northern Ireland and the rest of the UK after Brexit.
Boris Johnson has insisted the UK, including Northern Ireland, will leave the EU "whole and entire" after Brexit.
But Mr Corbyn claimed the report shows the Brexit deal will "separate Northern Ireland in practice from whole swathes of the UK's internal market."
"This is cold hard evidence that categorically shows the impact a damaging Brexit deal would have on large parts of our country," he said.
"This drives a coach and horses through the Prime Minister's claim there will be no border in the Irish Sea. It's simply not true."
The full contents of the document were not immediately revealed. But Mr Corbyn said: "What else are they hiding? What else will they sell you out on?"
Mr Corbyn said Johnson's promise to "get Brexit done" was a "fraud on the British people" leading to "Years of more painful negotiations and broken promises".
Even before today's event it was well-known that, despite Boris Johnson's claims, some checks will be needed on goods travelling to Northern Ireland.
Under the Prime Minister’s Brexit deal, Northern Ireland will share customs rules with the rest of the UK.
But when goods move into Northern Ireland across the Irish Sea from the rest of the UK, EU customs rules will apply to them - if they're deemed "at risk" of moving into the EU later on.
That means firms moving goods west from Britain to Northern Ireland will have to fill out two customs forms.
And already-public Government documents say this will lead to "additional administrative costs" on goods moving from east to west - estimated at around £15 to £56 per customs declaration.
Separately, under single market rules, firms will also face fees of at least 55 Euros (£47) at border inspection posts when sending "products of animal origin" from Britain to Northern Ireland, government documents say.
As for goods moving from west to east - from Northern Ireland to GB - Johnson has repeatedly said there will be no checks at all.
But there is conflicting information as his own Brexit Secretary has previously told MPs: "Exit summary declarations will be required in terms of NI to GB."
This breaking news story is being updated.
