Ireland will consider British proposals to reassure the Democratic Unionist Party on a border deal for Brexit – but will not agree changes “to the core” of a draft agreement which emerged on Monday.

That was the view of Minister for Foreign Affairs Simon Coveney who told the Dáil the Irish Government remained determined that “a hard border” cannot be put in place after the United Kingdom leaves the European Union.

The Tánaiste said the Irish Government would certainly look at any new proposals from British Prime Minister, Theresa May, aimed at overcoming the DUP’s objections to the draft deal allowing cross-border relations continue after Brexit happens.

“But our position is that the core meaning of the text we had on Monday needs to remain intact,” Mr Coveney said.

He was replying to Sinn Féin deputy leader, Mary Lou McDonald, who said her party had given the Government “qualified support” for its conduct of Brexit negotiations.

“Today we hear new and worrying language coming from the Government,” Ms McDonald referring to the Taoiseach’s statement that he would consider changes proposed by Mrs May.

“If the Tories want to sail off into the sunset away from the European Union, that’s their business. But the North of Ireland is our business,” she added.

Ms McDonald demanded a guarantee from Mr Coveney that the North remain part of the EU single market and customs union after Brexit. She also said the EU Court’s jurisdiction must remain in tact and the Good Friday Agreement must be respected.

But Mr Coveney said he had an obligation “not to stoke things up” in an already difficult situation.

“We will not support the re-emergence of a hard border,” he stressed.

“But I need to be cautious about what I say and how I say it,” the Tánaiste added.

In another Dáil exchange, Mr Coveney insisted moves towards greater EU defence cooperation does not amount to “joining an EU army.”

People Before Profit TD, Richard Boyd Barrett said Government moves to take Ireland into the EU’s Permanent Structured Cooperation (PESCO) programme breached the Irish Constitution and went against military neutrality.

Mr Barrett accused the Government of trying to “ram through” legislation permitting Ireland joining PESCO with a rushed and very limited debate. He said PESCO was being “touted” by EU leaders, Jean Claude Juncker and Donald Tusk, as “an EU army.”

But Mr Coveney said some TDs were trying to suggest PESCO was something more than it was in reality. He said the programme allowed countries to opt into certain things on a case by case basis.

Mr Coveney insisted that PESCO would allow cooperation on things like peacekeeping, counter terrorism, training and marine surveillance.

Mr Boyd Barrett said this was “cynical rubbish” and he challenged the Foreign Affairs Minister to publish Attorney General’s legal advice on the issue.

But the Minister for Foreign Affairs said Deputy Boyd Barrett knew this was not permitted.