The European Parliament is to call for Northern Ireland to stay in the single market and customs union in order to protect the integrity of the EU’s borders.

MEPs have concluded it is the best solution to the problem of ensuring there is no border in Ireland. The move has the support of all major non-eurosceptic political groups.

It would mean continued free movement on the island of Ireland, with customs checks instead taking place at ports on the Irish sea for visitors travelling between Great Britain and Northern Ireland.

The resolution, set to be voted on hours before Theresa May’s make-or-break Tory conference speech, rubbishes Britain’s existing proposals on the issue and is set to enrage DUP MPs propping up Ms May’s Government.

Only yesterday the EU’s chief negotiator Michel Barnier said not enough progress had been made on Europe’s key objectives – the financial settlement, EU citizens and Ireland – for the discussions to move on to the future trade deal the UK wants.

Both the UK and EU believe there should be no “hardening” of the border with the Republic, which is currently not policed – but disagree on how to do this while Ireland remains inside the EU’s borders and the UK leaves them.

The Independent understands that European Parliament chiefs believe shifting border posts to Irish sea ports is the optimal solution. One source said the EU’s physical border had to be somewhere and could not just have a gaping hole in it.

European Parliament Brexit chief Guy Verhofstadt (European Parliament)

The resolution rubbishes Britain’s proposals for an infrastructureless NI border based on spot checks and says that the UK plan for a lack of physical infrastructure “presumes that the United Kingdom stays in the internal market and customs union or that Northern Ireland stays in some form in the internal market and customs union”. The PM has ruled out keeping the UK as a whole in the customs union or single market.

At a press conference in Brussels today the European Commission’s chief Brexit negotiator Michel Barnier said the resolution was “important”, mentioning it alongside next month’s European Council meeting as one of the hurdles the UK would have to clear before it could progress to the next stage of talks.

The wide-ranging resolution, which covers the whole Brexit process so far, says the European Parliament “believes that it is the responsibility of the UK Government to provide a unique, effective and workable solution that prevents a “hardening’ of the border, ensures full compliance with the Good Friday Agreement in all its parts, is in line with European Union law and fully ensures the integrity of the internal market and customs union”.

The European Parliament is not involved in day-to-day negotiations with the UK but has a final veto on the ultimate Brexit deal which is agreed. The body’s Brexit steering group also meets regularly with Mr Barnier.

Brexit a waste of time and energy, European Parliament co-ordinator claims

The plan, which was published on Thursday, is almost certain to pass the parliament: it was signed by Guy Verhofstadt, the European Parliament’s Brexit coordinator and chair of the liberal group; Manfred Weber, chair of the conservative group; Gianni Pittella, chair of the socialist group; Gabi Zimmer, chair of the left group; and Philippe Lamberts and Ska Keller, the co-chairs of the green group. It is also backed by Danuta Hübner, chair of the Parliament’s committee on constitutional affairs.

Chief negotiator Mr Barnier today said Britain has not made “sufficient progress” in Brexit talks for trade or transition discussions to begin – despite Theresa May’s Florence speech having created “a new dynamic” in negotiations.

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Speaking at the end of the latest round, Mr Barnier told reporters in Brussels that clarity had been reached on a number of issues – but warned that the EU-imposed starting line to move to trade talks could still be months away.

The EU has consistently said it would not discuss the UK’s future relationship with the EU, which includes trade and transition periods, until “sufficient progress” has been made on what it calls “separation issues”.

Other than the Northern Ireland border, the EU wants to settle the rights of EU citizens living in Britain, and how much Britain will pay to cover its liabilities when it leaves the EU – before talks move on to their next phase and a transition deal or trade arrangements can be discussed.

Liberal Democrat Brexit spokesperson Tom Brake said: "To have one nation of the UK in the single market and the other three nations outside it would be a complication built upon a fiasco that could lead to the break up of the United Kingdom.

EU says no Brexit sufficient progress despite May speech

"It just shows how little thought, even now, the government has put into the sheer complexity of Brexit.

"There is a very simple solution: stay in the single market. Sadly the government would rather risk the break up of the UK just so it can hurl a few stones at the EU. It is utterly pathetic."

A British Government spokesperson said: " We recognise and respect the vital role the European Parliament will play in this process. However, this is a draft document and was issued before negotiations this week were completed. Therefore it does not take into account the further progress made this week.

" We and the EU have committed to protecting the Belfast Agreement and the Common Travel Area and agree that we will not accept any physical infrastructure at the border.