DUP leader Sir Jeffrey Donaldson has insisted that the UK Government and European Union must renegotiate the Northern Ireland Protocol.
Sir Jeffrey took part in a virtual meeting with European Commission vice president Maros Sefcovic on Monday morning.
He described his message to Mr Sefcovic as “simple – the protocol has not worked”.
The protocol was negotiated as part of the Brexit settlement to avoid a hard border on the island of Ireland.
Unionists strongly oppose the additional checks on goods arriving into Northern Ireland from the rest of the UK as undermining the union.
Leading supermarkets at the weekend hit out over fears of the impact on supply lines into the region once various grace periods on checks end.
Sir Jeffrey said: “The barriers and distortion to trade within the UK internal market brought about by it must be swept away and not replaced.
“We have pressed the UK Government to that end. Both the Government and the EU must now renegotiate.”
Sir Jeffrey said if the EU is “unwilling to recognise the harm caused by the Protocol” then the UK Government “must take appropriate unilateral action using Article 16”.
“Subjecting Northern Ireland to laws and regulations upon which its representatives and Westminster has no say can never work and does not have the support of both communities,” he added.
Speaking earlier, Sir Jeffrey also accused the EU of “destabilising and undermining” the power-sharing arrangements at Stormont, by Northern Ireland politicians having no say in post-Brexit arrangements.
Last week the DUP set out seven tests on the Protocol.
They include a promise of no checks on any sort of goods being sent to Northern Ireland from Great Britain and compatibility with the Act of Union which says all parts of the UK should be on equal footing when it comes to trade.
However Sinn Fein president Mary-Lou McDonald said any thought of changing the protocol is “fanciful”, adding it is “here to stay”.
She described the protocol as “the answer, not the problem”.
“The protocol isn’t going anywhere, it has been negotiated, it has also been signed off not just by the European side but also by the British Government, so I think, with respect, any assertions that the protocol can be abolished are fanciful, that’s not going to happen,” she told reporters in Belfast.
“There are issues and challenges that have arisen with the protocol, they need to be addressed and the place to address them is in the joint committee.
“The protocol is necessary and it’s not going anywhere.
“I think the DUP, Jeffrey Donaldson and others need to come to terms with that.”
Ms McDonald also warned that any unilateral action from the UK side would not be acceptable