Northern Ireland could remain an effective member of the customs union and the single market as part of the UK’s Brexit deal with the EU, according to an MEP.

Belgian Philippe Lamberts said on Monday the draft text of the deal expected to be agreed on Monday would see almost “full alignment” between Northern Ireland and the Republic of Ireland.

The Irish government has said it will not agree to any deal that would see physical checks on the border amid fears it could endanger the Good Friday Agreement.

But such a deal could effectively see the EU border erected in the Irish Sea between the island of Ireland and mainland Britain.

The Democratic Unionist Party (DUP), which props up Theresa May’s minority government, has previously said it would reject any such proposal.

Lamberts told Sky News: “The British government would commit to maintain full alignment of legislation, where pertinent of course, so single market and customs union legislation, that might potentially create a border, will remain fully aligned so there is not.”

He added: “That’s the only solution if you want to keep the Good Friday Agreement.”

The draft text of the agreement seen by RTE states:

“In the absence of agreed solutions the UK will ensure that there continues to be no divergence from those rules of the internal market and the customs union which, now or in the future, support North South cooperation and the protection of the Good Friday Agreement.”

Shortly after the reports emerged, Downing Street said May would not agree to any deal that led to an economic border between Northern Ireland and the rest of the UK.

“The prime minister has been clear that the UK is leaving the EU as a whole, and the territorial and economic integrity of the UK will be protected,” spokesperson for the prime minister said.

Sammy Wilson, the DUP’s Brexit spokesman, told the Press Association, the deal looked like Dublin “trying to push the UK government into a corner in the negotiation”.

“It is not well thought through. I don’t think, given its promises, the British government could concede on this,” he said.

And Lord Trimble, the former Northern Ireland first minister and leader of the Ulster Unionist Party, told the BBC Radio 4′s World at One programme the agreement was “potentially very bad news for Northern Ireland”.

“That would put Northern Ireland businesses at a huge disadvantage and this isn’t just a minor thing – 80% to 90% of Northern Ireland’s business is done with and through the rest of the United Kingdom,” he said.

“So it’s that 80% to 90% that is going to be harmed by being clip-locked into European regulation while other people are free from that and the country as a whole is free to work out what it’s regulatory provisions are.”

The prospect of Northern Ireland remaining an effective member of the customs union and single market also caused Nicola Sturgeon to question why Scotland could not do the same.

May is holding crunch talks in Brussels today in order to hammer out a deal on the Northern Ireland border, citizens’ rights and the UK’s divorce bill.

The EU has refused to progress talks to phase two, negotiations on a future trade relationship, until those three issues are settled.