Jeremy Corbyn has accused Boris Johnson of throwing Northern Ireland "under a bus" as the Prime Minister insisted his Brexit deal was a “great advance for the whole of the UK”.

At a raucous PMQs the Labour leader clashed with Mr Johnson over post-Brexit workers' rights, environmental standards and the future of the NHS.

But Mr Corbyn sought to pin the PM down on the issue of Northern Ireland’s relationship with Great Britain post-Brexit, telling Mr Johnson how less than a year ago he said: “’Regulatory checks and…customs controls between Great Britain and Northern Ireland would damage the fabric of the Union.’

“Given this deal clearly does damage the fabric of the Union, does he still agree with himself?” asked the Labour leader.

The PM insisted, under the UK-EU deal, the Union would be preserved and more than that the country could go forward as one United Kingdom to do trade agreements in a way that would have been impossible under previous deals.

“This is a great advance for the whole UK,” declared Mr Johnson, ”and we intend to develop that together with our friends in Northern Ireland.”

But he took the Labour leader to task, saying, to Tory hear hears: “It is a bit rich to hear from him about his sentimental attachment to the fabric of the Union between Great Britain and Northern Ireland when he has spent most of his political lifetime supporting the IRA and those who would destroy it by violence.”

Referring to the “very real border down the Irish Sea” created by the deal, Mr Corbyn noted how on Saturday the PM told MPs there would be no checks on goods moving between Northern Ireland and Great Britain yet he pointed out yesterday Stephen Barclay, the Brexit Secretary, confirmed to peers Northern Irish businesses sending goods to Britain would indeed have to complete export declaration forms.

“Is the Prime Minister right on this or is the Brexit Secretary right? They cannot both be right,” insisted Mr Corbyn.

Mr Johnson boasted the UK would be “preserved whole and entire” by the Brexit deal and the country would as one entity be able to do free trade deals.

“There will be no checks between Northern Ireland and GB and there will be no tariffs between Northern Ireland and GB because we have protected the customs union,” insisted the PM.

“This lachrymose defence of the Union comes a little ill from somebody who not only campaigned to break up the Union between Great Britain and Northern Ireland by his support of the IRA but also wants to spend the whole of the next year not just on a referendum on the EU but on another referendum on Scotland.

“That is what he wants. This is the threat to our United Kingdom; the Labour front bench,” insisted Mr Johnson.

Questioning whether the PM had read his own Government’s bill, the Labour leader said: “This is the Prime Minister, who unlawfully prorogued Parliament, said he would refuse to comply with the law, threw Northern Ireland under a bus, ripped up protections for workers’ rights and environmental standards, lost every vote along the way and tried to prevent genuine democratic scrutiny and debate.

“He once said the ‘whole Withdrawal Bill, as signed by the previous Prime Minister, is a terrible treaty,’ yet this deal is even worse than that. Even if he is not that familiar with it, does he accept Parliament should have the necessary time to improve on this worse-than-terrible treaty?”

Mr Johnson told MPs Labour had claimed: the Government could not reopen the Withdrawal Agreement and it did; could not get rid of the backstop and it did; could not get a new deal and it did; could not get it passed by Parliament and it did.

“This is the party that delivers on Brexit and delivers on the priorities of the British people,” added the PM.