Intense Brexit negotiations are continuing in Brussels this weekend after Boris Johnson proposed a compromise to break the deadlock.
Sky News understands the prime minister’s plan would involve Northern Ireland continuing to administer European Union tariffs despite leaving the bloc’s customs union.
This would remove the need for customs checks but also allow the businesses north of the border to benefit from new UK trade deals by applying for a rebate from the government.
Downing Street has not officially confirmed the plan but Mr Johnson stoked speculation on Friday by refusing to say whether Northern Ireland would stay in the EU customs union.
“I can certainly tell you that under no circumstances will we see anything that damages the ability of the whole of the United Kingdom to take full advantage of Brexit,” the prime minister said.
The plan would potentially see some customs checks taking place in the Irish Sea on goods flowing between Northern Ireland and the rest of the UK.
That could cause concern among unionist politicians who want Northern Ireland to leave the EU on the same terms as the rest of the country.
Speaking on Friday, DUP leader Arlene Foster said: “We have been consistent in our opposition to the backstop, whether UK or Northern Ireland only.
“Anything that traps Northern Ireland in the European Union, whether single market or customs union, as the rest of the United Kingdom leaves will not have our support. The prime minister is very mindful of that.”
Eurosceptic Conservative MPs have indicated they would be prepared to back a deal if the DUP also supports it.
“I suspect if the DUP is on board, fewer than seven Tory MPs will vote against”, said one.
However, another senior Brexiteer said he did not think the EU would agree to the new plan, equating it to former prime minister Theresa May’s failed ‘Chequers’ proposal.
“I don’t think they’ll do that, it’s not where they are at,” he said.
The proposal from Mr Johnson would replace the controversial backstop, the insurance policy aimed at avoiding a hard Irish border, which has proved the sticking point in negotiations.
The EU’s chief Brexit negotiator Michel Barnier has said talks were intensifying “in a constructive spirit” and that Brussels “will do everything it can for an agreement, fully in line with our principles”.
Ambassadors from the 27 remaining EU nations will meet on Sunday to discuss progress in the talks ahead of a leader’s summit on Thursday.