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MPs have swiftly dismissed the EU's latest effort to secure a Brexit deal after the bloc said the UK could be allowed to leave the customs union of its own accord in a backstop scenario.

The proposed concession came from EU Brexit negotiator Michel Barnier just days before a second meaningful vote on Theresa May's Brexit deal in the House of Commons.

It has previously been suggested that both the EU and the UK would have to agree for Britain to be able to fully leave the customs union in a backstop scenario.

However, the EU would now be willing to allow the UK to fully leave the customs union unilaterally - provided it avoids a hard border between Ireland and Northern Ireland.

"The UK will not be forced into a customs union against its will," Mr Barnier said. "The EU will continue working intensively over the coming days to ensure that the UK leaves the EU with an agreement."

He stressed that Britain would still need to keep the sensitive border between EU member state Ireland and the UK province of Northern Ireland free of controls.

In a series of messages on Twitter, Mr Barnier also said the EU had proposed a "legally binding interpretation" of the Withdrawal Agreement.

He said arbitration panel envisaged the deal would give the UK the right to a "proportionate suspension of its obligations under the backstop, as a last resort" if the EU breached its obligations to use "best endeavours" and act in "good faith" to negotiate alternative solutions.

The EU was also ready to give "legal force" to the commitments made in January's letter from Donald Tusk and Jean-Claude Juncker, writing them into a "joint interpretative statement".

However, following Mr Barnier's comments on the customs union DUP deputy leader Nigel Dodds said his proposal regarding the Northern Ireland backstop was neither "realistic nor sensible".

"It disrespects the constitutional and economic integrity of the United Kingdom," he said.

"This is an attempt to get ahead of a possible blame game and appear positive when in reality it is going backwards to something rejected a year ago."

Brexit Secretary Stephen Barclay also dismissed Mr Barnier's proposal.

He tweeted: "With a very real deadline looming, now is not the time to rerun old arguments. The UK has put forward clear new proposals. We now need to agree a balanced solution that can work for both sides."

The development comes after the Prime Minister have a speech warning warning the UK will be plunged into crisis if MPs reject the Withdrawal Agreement at the upcoming vote.

She said "no-one knows" what will happen if her plan is defeated, with the possibility of Brexit being derailed completely.

Mrs May said both the democratic and economic cases for backing her deal are "clear" as she issued a plea to MPs of: "Let's get it done."

The Prime Minister had also used her speech in Leave-supporting Grimsby to both urge the European Union to give ground on the Northern Ireland backstop.

She also called on Tory Eurosceptics to recognise failure to back the deal could result in a softer Brexit or another referendum.

"Next week, MPs in Westminster face a crucial choice: Whether to back the Brexit deal or to reject it," she said.

"Back it and the UK will leave the European Union. Reject it and no-one knows what will happen.

"We may not leave the EU for many months, we may leave without the protections that the deal provides. We may never leave at all."

If the Prime Minister’s deal is passed, she may still need to extend article 50 in order to make arrangements for the current Brexit date of March 29.

Mrs May is due to speak to EU leaders by telephone over the weekend and a European Commission spokesman said "intensive work" was going on between London and Brussels.

It is unsure what could happen if the vote fails and this would leave Parliament searching for an alternative in time for the looming deadline.

Any extension to the article 50 process requires unanimous agreement from the rest of the EU.