Theresa May said her Brexit plans will not be “derailed” as senior ministers prepare to consider the future shape of the UK’s relationship with the EU.
She said talks would now begin on an “implementation period” immediately after the formal date of Brexit.
But some Tory Eurosceptics have already warned they will not accept arrangements which resemble continued EU membership during the transition to a new relationship.
Boris Johnson called for Mrs May to strike a deal with Brussels that would allow the UK to ditch EU laws, warning that being unable to diverge from the bloc’s regulations would leave the UK a “vassal state”.
Writing in the Sunday Telegraph, Mrs May said: “Amid all the noise, we are getting on with the job.
“In the face of those who want to talk Britain down, we are securing the best and most ambitious Brexit deal for our whole United Kingdom.
“And my message today is very clear: we will not be derailed from this fundamental duty to deliver the democratic will of the British people.”
The Cabinet will thrash out its stance on a post-Brexit trade deal over the coming days, with Mrs May under pressure from Brussels to provide clarity on the UK’s desired “end state” for the relationship it wants with the EU.
The Brexit “war cabinet” – a sub-committee of senior ministers chaired by Mrs May – will meet on Monday, with a meeting of the full Cabinet scheduled for Tuesday.
Mr Johnson used a Sunday Times interview to set out his vision for a UK-EU trade deal that would “maximise the benefits of Brexit” by allowing Britain the freedom to diverge from Brussels’ laws.
He called for a deal that “gives us that important freedom to decide our own regulatory framework, our own laws and do things in a distinctive way”.
Meanwhile, behind-the-scenes efforts to prevent a humiliating second Commons revolt appear to have resulted in a situation which will see March 29 2019 written into the Government’s Brexit legislation.
It will be as Mrs May promised, but with flexibility allowing the date to be changed if negotiations with Brussels look set to stretch beyond that date.
Rebels who helped inflict Mrs May’s first Commons defeat on Wednesday lined up behind the compromise, which has been put forward by prominent backbenchers on both sides of the EU referendum divide.
The Government is understood to be “looking closely” at the amendment tabled by MPs including Remain supporter Sir Oliver Letwin and Brexiteer Bernard Jenkin – which would give ministers flexibility to change the departure day if
The Government has not formally supported the move but it would appear certain to back the measure if it presented a way for Mrs May to avoid another Commons reverse.
Former Cabinet minister Nicky Morgan, one of the rebels who helped inflict Mrs May’s first Commons defeat, gave her support to the compromise over the Brexit date.
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She said the new amendment “demonstrates how all Conservative MPs can work together” to deliver the best possible Brexit and reflects the flexibility within the Article 50 withdrawal process.
The amendment also emphasises that “Parliament will be fully involved in Brexit”, she said.