Northern Ireland Secretary Julian Smith has denied that the UK government is proposing customs centres at locations away from the border.
"I don't know where these papers have come from that were reported on yesterday, I've not seen them, I don't know who's written them, but I'm clear that we can't have customs facilities in the places mentioned in the reports," he said.
"And I'm clear that the prime minister is fully committed to the Good Friday Agreement."
Mr Smith told BBC Radio Ulster: "Five or ten miles from the border is still an issue and I am clear on that, and the government is clear that the Good Friday Agreement needs to be respected."
This morning, Tánaiste and Minister for Foreign Affairs Simon Coveney flatly dismissed the proposal saying in a tweet that it was "a non-starter".
Meanwhile, British Prime Minister Boris Johnson said the "non-paper" contained preliminary ideas that had been floated and the formal proposals would be set out very shortly - widely expected to be later this week, after the Tory conference finishes tomorrow.
"They are not talking about the proposals we are going to be tabling, they are talking about stuff that went in previously," he told the BBC.
"But clearly this is the moment when the rubber hits the road. This is when the hard yards really are in the course of the negotiations.
"The difficulty really is going to be around the customs union and to what extent Northern Ireland can be retained within EU bodies at all.
"We're going to make a very good offer, we are going to be tabling it very soon, but there is a difficulty if you try to keep Northern Ireland in a customs union because one of the basic things about being a country is you have a single customs perimeter and a single customs union."
In an indication of why the UK has delayed tabling its formal proposals, Mr Johnson said there was a risk that critics could "needlessly distort" what was being put forward.
Mr Johnson urged the European Union to work with him on efforts to reach a Brexit deal when he presents formal proposals to break the deadlock within days.