The DUP leader Arlene Foster has said her party will "not countenance" any Brexit arrangement that could lead to a new border between Northern Ireland and Britain.
The DUP East Antrim MP Sammy Wilson has also warned that any British government proposal to "placate Dublin and the EU" would mean the end of the DUP's agreement to prop up Theresa May's Conservative administration.
Amid reports that Dublin and London could be close to a deal that would avoid a “hard border”, Ms Foster went on the offensive to insist that she will not accept a new border “in the Irish Sea”.
"The United Kingdom voted to the leave the European Union as one nation and we are leaving as one nation," she said on Thursday.
Ms Foster said that Ms May already “has been categorical” in accepting the DUP requirement. “Her Majesty’s government have a clear understanding that the DUP will not countenance any arrangement that could lead to a new Border being created in the Irish Sea,” she said.
Ms Foster issued her statement after a London Times report about a possible Brexit deal caused alarm in some DUP circles. The report said the British and Irish Governments were close to a deal that would "avoid regulatory divergence" between the North and South.
Ms Foster said: “As the EU exit discussions continue, there will be from time to time speculation, some of which is ill-informed, from those not across the details.
"For our part we remain focused on ensuring that as we leave the European Union we achieve an outcome that is beneficial to Northern Ireland and the United Kingdom as a whole," she added.
Ms Foster said the DUP was in “constant contact” on Brexit issues with the British government.
“During our discussions, we reiterated that United Kingdom/Republic of Ireland arrangements may be necessary as we exit the EU but there can be no arrangements agreed that compromise the integrity of the UK single market and place barriers, real or perceived, to the free movement of goods, services and capital between Northern Ireland and the rest of the United Kingdom.
“We support the continuance of the common travel area for the movement of people between the United Kingdom and the Republic of Ireland.”
The DUP leader said she looked forward to the “European discussions being able to move to the second stage to deal with trading arrangements between the UK and the EU27”.
Meanwhile, DUP MP Sammy Wilson responded to the London Times report about a possible Brexit deal that would involve devolving powers to a Northern Executive to facilitate North-South-EU regulatory convergence in areas such as agriculture and energy.
Such an arrangement would be unworkable, he told BBC Radio Ulster. He said the DUP was seeking clarification with the British government on the report.
“If there is any hint that in order to placate Dublin and the EU they’re prepared to have Northern Ireland treated differently than the rest of the UK, then they can’t rely on our vote,” he said.
“They have to recognise that if this is about treating Northern Ireland differently or leaving us half in the EU, dragging along behind regulations which change in Dublin, it’s not on.”
In return for the support of the DUP’s 10 Ps the British government is committed to providing an extra £1 billion in funding to Northern Ireland along with flexibility in how another £500 million of the annual London subvention to Northern Ireland is spent.
