Britain is facing demands to push back the ‘cut-off date’ for new EU migrants to 2021 in return for a two-year transition deal, it emerged last night.

Documents show that EU negotiators plan to issue the demand during the next phase of negotiations in return for the ‘transition deal’ wanted by the Prime Minister.

The ultimatum risks infuriating Brexiteers who insist that Brexit should be capitalised on by the Government to regain control of the country’s immigration system.

The Brexit divorce deal agreed by Theresa May last week proposes a ‘cut-off date’ of March 2019, after which new EU migrants would lose the automatic right to reside in the UK on a long-term basis.

Britain is facing demands to push back the ‘cut-off date’ for new EU migrants to 2021 in return for a two-year transition deal, it emerged last night (file photo)

British officials insist the issue has been largely settled in negotiators, the EU believes that the date can be pushed back even further in talks to grants Mrs May a transition deal.

An EU document said: ‘In such case, the ‘specified date’ should, in the Commission’s view, be defined not as the date of the United Kingdom’s withdrawal, but as that of the end of the transitional period.’

The revelation was contained in a ‘state of progress’ report sent by the European Commission to the European Council setting out negotiating issues before EU leaders meet to discuss trade talks on Thursday.

The strategy will raise concerns that Brussels is planning to use the next phase of discussions, likely to be given the green light by leaders during the meeting, to ask for more demands on so-called divorce issues.

The move came as Tory MPs united behind Mrs May in the Commons as she outlined details of the deal.

The PM confirmed that the deal involves a controversial divorce payment of up to £39 billion.

But she said the offer would be ‘off the table’ if the EU refuses to agree a comprehensive trade deal.

Mrs May also dismissed claims that the deal would force the UK to shadow EU laws. Asked if the UK would regain ‘full regulatory autonomy’, she said: ‘That is the whole point. Once outside we will be able to determine our regulation and where we want to diverge from the EU.’

Documents show that EU negotiators plan to issue the demand during the next phase of negotiations in return for the ‘transition deal’ wanted by the Prime Minister

Outlining the deal, she added: ‘This is good news for people who voted leave, who were worried that we were so bogged down in tortuous negotiations that it was never going to happen, and it is good news for people who voted remain, who were worried that we would crash out without a deal.

‘We are going to leave, but we will do so in a smooth and orderly way, securing a new deep and special partnership with our friends while taking back control of our borders, money and laws once again.’

Unusually, Mrs May won support from both sides of the Tory Brexit divide.

Former minister Anna Soubry, one of the leading anti-Brexit rebels, welcomed the deal as a ‘major step forward’, and said there was ‘complete unanimity’ in the party behind the PM.

But Mrs May was also backed by former leader Iain Duncan Smith, who warned last week that Mrs May would have to walk away from the talks unless Brussels agreed to ‘back off’ from its most extreme demands.

The Brexit divorce deal agreed by Theresa May last week proposes a ‘cut-off date’ of March 2019, after which new EU migrants would lose the automatic right to reside in the UK on a long-term basis

Mr Duncan Smith congratulated Mrs May on ‘driving through an improved agreement’ with Brussels.

Fellow Tory Nick Boles likened the Prime Minister to a former England cricketer, telling MPs: ‘I’m no cricket fan but may I tell her that that was a performance worthy of Geoffrey Boycott?’

Former Conservative chancellor Lord Lawson struck a more cautious note, saying there were still ‘important issues to resolve’. But he added: ‘It’s just about acceptable.’

Tory MP Philip Davies, another Eurosceptic, questioned the wisdom of handing billions to Brussels at a time of austerity at home.

‘The Prime Minister said that there had been give and take in these negotiations, of course she’s absolutely right. We’re giving the EU tens of billions of pounds and they’re taking them,’ he said.