The Brexit deal negotiated by Theresa May could see Britain tied to EU rules until after the next general election, under proposals being considered by negotiators.

The plans, discussed by EU27 ministers in Brussels on Monday, open the door to an incoming government reversing Brexit before the UK has fully left the bloc’s orbit.

Michel Barnier confirmed on Monday morning that EU leaders are in discussions about a one-time, fixed length extension to the transition period during which all EU rules continue to apply to Britain.

He said “all the governments have agreed to the principle of a possible extension” but that the date it could run to is not yet fixed.

Reports over the weekend suggested that, behind closed doors, Mr Barnier is pushing for 2022 as the end date, though he said “no decision has been made yet”.

The controversial draft withdrawal agreement published last week includes provisions for a transition extension but lists the date as 20XX – with the XX to be filled in later.

“I think it’s rather sensible to keep the possibility for a one-off extension for a limited time should this become necessary,” Mr Barnier said.

All the governments have agreed to the principle of a possible extension Michel Barnier, EU chief Brexit negotiator

“We will make a final and specific proposal for these purposes during the course of this week.”

Downing Street has previously said it is open to extend the transition, but suggested it would only be extended for “a matter of months”, declining to be more specific.

That “matter of months” now appears to be two years – a period that would extend the transition to six months after the next scheduled election in May of that year.

Ms May, speaking at the CBI conference, said it was “important” that the UK had escaped EU rules by the 2022 election, but did not give a guarantee.

Negotiations are continuing to agree a final end date before the EU Council next Sunday, which is intended to sign off the withdrawal agreement.

The prime minister told a questioner: "From my point of view, I think it is important in delivering for the British people that we are out of the implementation period before the next general election."

The possibility that it would continue into the next parliament will enrage Brexiteers, who fear that it would give an incoming government a platform to reverse Brexit or sign up to a close Norway-style relationship like the European Economic Area, with no break.

Mr Barnier also confirmed on Monday morning that any extension would require the UK to pay a much higher Brexit divorce bill.

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“All I can say is that at this stage if the extension were to be enacted, if the UK were to remain a part of the customs union for an extended period of time, we would have to have an agreement to the financial contribution to the EU,” he told reporters in Brussels.