Brexit Minister Stephen Barclay has accused the EU's chief negotiator of trying "to rerun old arguments", as talks continue between the UK and EU.
According to him, Great Britain would be free to leave the suggested single customs territory, aimed to avoid a physical border with Ireland.
But the authorities and the DUP have rejected this, because then Northern Ireland would have to remain within the EU customs territory.
Stephen Barclay stressed that Great Britain would be able to exit the single customs territory unilaterally if it chose to do so.
"With a very real deadline looming, now is not the time to rerun old arguments. The UK has put forward clear new proposals. We now need to agree on a balanced solution that can work for both sides," he tweeted recently.
The UK is set to leave the bloc on 29 March, but the House of Commons hasn't approved a new deal following the rejection of May's agreement with Brussels in January.