The DUP has warned Theresa May against any Brexit deal that creates a customs or regulatory border down the Irish Sea, threatening to withdraw support for her government. The party's deputy leader, Nigel Dodds, said any backstop to prevent a hard border must be "crystal clear" and time-limited.
"The danger of this Irish backstop has the potential to not only separate Northern Ireland from the rest of the United Kingdom and any future diversion there may be from it, but it also has the potential to shackle the United Kingdom for generations to come in its relationship with Europe.
“The DUP will not be signing up to any backstop unless we ensure that every line of it complies with our requirements,” he told a fringe meeting at the Conservative Party conference in Birmingham.
The DUP’s warning to the prime minister came as the British government is preparing to make its own proposal on the backstop, which would accept the need for regulatory divergence between Northern Ireland and the rest of the UK.
DUP leader Arlene Foster said any agreement that would separate Northern Ireland from the rest of the UK would be an unacceptable violation of the constitutional integrity of the UK.
“We cannot have either a customs border down the Irish Sea or a regulatory border because that would make us separate from the rest of the United Kingdom, and that doesn’t work from a constitutional perspective and it doesn’t work from an economic perspective either,” she told Bloomberg TV.
“That would impede the constitutional integrity of the United Kingdom. And the prime minister has been very clear, she is a unionist, she believes in the union of the four countries of the United Kingdom, and therefore there can be no borders, whether of a regulatory nature or of a customs union nature either.”
Ms Foster and Mr Dodds held talks with Mrs May in Birmingham on Tuesday, and the DUP leader said they would remain in close contact as the Brexit negotiations entered their final phase.
"We do recognise that we are reaching a crunch time in the negotiations in relation to our leaving of the European Union. Therefore it's important that we continue to have those conversations, and it's important that we understand what the proposals are."