The DUP is urging Westminster MPs to support its campaign to have the Northern Ireland protocol scrapped.
Senior party figures including leader and NI first minister, Arlene Foster, have written to all MPs asking them to attend a debate on the protocol on Monday.
The protocol is part of the Brexit deal which kept NI in the EU’s customs union to prevent a hard land border on the island of Ireland.
Instead, new checks were implemented at Belfast and Larne ports because the EU and UK now follow different customs rules.
It has created a de facto border down the Irish Sea between NI and Great Britain, resulting in some trade disruption.
Earlier this month the DUP, whose MPs voted for Brexit but then opposed the protocol, launched an official campaign to have the mechanism axed.
In its letter published this week, the party said its decision was fuelled by the European Commission’s brief threat of triggering of Article 16.
But the party had also been under increasing pressure from its grassroots supporters, who say the protocol poses an existential threat to NI’s constitutional place within the UK.
“The actions and statements of the commission have caused very significant anger and harm within Northern Ireland,” the letter states.
“[This] compounded the notion that the EU is playing fast and loose with Northern Ireland, attempting, on the one hand, to require the UK government to enforce its obligations whilst being prepared to waive elements of the protocol when it suits the needs of the EU,” it added.
The letter also sets out a range of trading areas the party says have been disrupted since the protocol took effect at the beginning of January and calls for its replacement.
Opposition parties in NI have accused the DUP of showing little effort in trying to find workable solutions to trade disruption.
The EU Commission and the Republic of Ireland government, which played a key role in the Brexit talks, have both said the NI protocol will not be removed.
Prime minister Boris Johnson previously said he would be willing to trigger Article 16, which undoes the protocol, if trade problems persist, although neither he nor the DUP has outlined what might replace it.
When announcing its campaign on 2 February, the DUP launched an online e-petition for a debate on the protocol in parliament, which has now received 140,000 signatures.
Ms Foster said the petition had received support from people in every constituency across the UK.
This week’s letter calls for the government to urgently take action to ensure unfettered trade is restored between Great Britain and NI.
European Commission vice president Maros Sefcovic is due to hold virtual meetings with a range of groups in NI on Thursday.
NI has remained in the single market for goods, so products entering the region from Great Britain must comply with strict EU rules on animal and plant health.
The full range of checks has not yet been implemented with a number of grace periods still running.
Additional reporting by Press Association
