Brexit talks have run into a ‘significant problem’ over the issue of the Northern Ireland border, Government sources have said.
Theresa May's leadership and her plans for Brexit are under pressure after a setback in talks with Brussels.
A hastily arranged meeting between Brexit Secretary Dominic Raab and European Union negotiator Michel Barnier failed to produce a breakthrough, leaving the process on a knife-edge ahead of a crunch summit on Wednesday.
The impasse over measures to prevent a hard border with Ireland has thrown the timetable for reaching a Brexit deal into doubt.
Following the meeting in Brussels, Mr Barnier said that ‘despite intense efforts’ there had been a failure to reach agreement on one of the trickiest aspects of the negotiations.
EU negotiators are said to be demanding a ‘backstop to the backstop’ to prevent a return of a ‘hard border’ between the North and the Irish Republic.
Theresa May has proposed that the backstop - which would effectively keep Northern Ireland in the single market while a permanent solution is found - should apply to the whole of the UK.
However it is understood the EU is insisting it should be backed up by the original Northern Ireland-only backstop which risks imposing a ‘border in the Irish Sea’ - something Mrs May has said is unacceptable.
The surprise announcement of the meeting fuelled rumours a deal was set to be done ahead of this week's summit of EU leaders.
The UK Government said there were still ‘unresolved issues’ relating to the backstop but it remained committed to making progress at the European Council meeting.
But with Mrs May under siege from Tory Eurosceptics and her DUP parliamentary allies, the Government also has a reason to appear to be taking a tough line.
The Prime Minister's room for manoeuvre is severely restricted, with opposition to both the EU's proposed backstop and concerns about her own alternative.
The EU version, which would see just Northern Ireland remain aligned with Brussels' rules, has been called unacceptable by Mrs May and is loathed by the DUP.
A special EU summit pencilled in for November to sign off a Brexit agreement could instead end up being used as an emergency meeting to discuss ‘no-deal’ plans.