Arlene Foster has said that it “may well be the case” that Article 16 is invoked over the Northern Ireland protocol ahead of her final meeting with Boris Johnson as First Minister.
Mrs Foster met with the Prime Minister for the last time after announcing her resignation last month.
And she did not back away from suggestions that the clause in the Withdrawal Agreement, which could allow for customs checks at the border between Great Britain and Northern Ireland to be suspended, could be put into action.
Customs checks on goods moving between Great Britain and Northern Ireland have caused problems for businesses on both sides of the border, ministers have said.
And under the agreement with the EU, one side is able to suspend parts of the border arrangements if they are found to cause significant economic, societal or environmental difficulties.
However this is only supposed to be invoked when all other options have been exhausted and is seen as a nuclear option.
Speaking outside Downing Street in London prior to meeting Mr Johnson, Mrs Foster said the PM needed to “deal with” the Northern Ireland protocol which she fears will “narrow common ground” if not addressed.
She said: “I think the Prime Minister and (Brexit minister) Lord Frost have been listening, they have been putting out some very good statements in relation to dealing with the protocol.
“But now we need to see action, and we need to see action quite soon, because every day the protocol remains the way it is, there’s more damage done to Northern Ireland.”
Asked whether she felt Mr Johnson had betrayed her over the border issues, having previously pledged never to create economic barriers between Northern Ireland and the rest of the UK, Mrs Foster said: “Well, look, I got into politics to make Northern Ireland a better place, to move Northern Ireland forward.
“I believe if we are to do that and continue to do that, then I think we need to deal with the protocol in a very proactive way and I hope that when I speak to the Prime Minister this morning we’ll hear more about that.”
But she was insistent that Brexit and the protocol needed to be viewed as separate issues.
“I think you have to separate Brexit and the protocol,” she said.
“The protocol is doing the damage to Northern Ireland.
“Of course I believe in Brexit because I believe that we needed to leave the European Union and all of the stringent rules that were there, to allow us to be more flexible, to allow us to have a place in the world.
“But if the United Kingdom is to have a new place in the world, Northern Ireland must be part of that and at present, because of the protocol, we’re not.”
Asked whether Article 16 of the protocol could be triggered, Mrs Foster said that “may well be the case”.
“We’ve said all along, when the European Commission tried to invoke Article 16 at the end of January, that the Europeans were quite happy to do it in terms of vaccines and making sure that they had enough vaccines,” she said.
“This is doing real damage to Northern Ireland in terms of our trade, but also in terms of the union and therefore the Prime Minister needs to act and I hope that Lord Frost will bring forward proposals very, very soon.”
The Northern Ireland Protocol is fiercely opposed by unionists and loyalists over its requirement for additional checks on goods arriving into the region from Great Britain regarded as a border down the Irish Sea.
New DUP leader Edwin Poots has vowed to get rid of the protocol.