Theresa May’s Brexit deal will have equivalent cost of losing the economic output of Wales or the City of London, research suggests.

The prime minister will plead with MPs to back her deal in a Commons statement on Monday afternoon.

A report by the the National Institute for Economic and Social Research (NIESR) said May’s plan will reduce the value of the UK economy by 3.9% – or £100bn a year by 2030 – compared to staying in the EU.

According to the study, this would be an average cost of more than £1,000 a person.

The NIESR study, which will be launched today by the People’s Vote campaign that wants a second referendum, said a no deal exit would reduce GDP by 5.5 per cent, or £140bn a year.

On Sunday EU leaders endorsed the agreement at an emergency summit in Brussels.

But the prime minister faces an uphill battle to win the vote in the Commons – due to take place in December.

In a statement to parliament today, May will tell MPs there is “not a better deal available”.

“We can back this deal, deliver on the vote of the referendum and move on to building a brighter future of opportunity and prosperity for all our people,” she will say.

The PM will warn parliament that if her deal is rejected then they will be “back to square one”.

European leaders yesterday all warned that there was not a better deal that could be negotiated. 

Around 90 Tory backbenchers have indicated they will oppose the deal. Labour also plans to vote against it.

Jeremy Corbyn said the deal was the “result of a miserable failure of negotiation that leaves us with the worst of all worlds”.

“Labour will oppose this deal in parliament. We will work with others to block a no deal outcome, and ensure that Labour’s alternative plan for a sensible deal to bring the country together is on the table,” he said.

Foreign Secretary Jeremy Hunt admitted yesterday the government could collapse if it lost the vote.

Asked if she would be duty bound to resign should the Commons reject her plan, May said yesterday: “It’s not about me.”

The prime minister has repeatedly refused to rule out quitting if she fails to win support for her Withdrawal Agreement.

DUP leader Arlene Foster also confirmed her party will not support the agreement.

And she warned she could pull the plug on the DUP’s confidence and supply agreement with the Tories should it pass.