The DUP leader has challenged the UK Government to meet seven tests for post-Brexit settlement arrangements.
Sir Jeffrey Donaldson said they must be compatible with the Act of Union and contain no new checks on goods being traded between Northern Ireland and Great Britain.
Unionists have voiced anger at the Northern Ireland Protocol which currently demands a swathe of new checks on goods arriving from Great Britain, claiming they are undermining the union.
Demonstrations have been held against the so-called border in the Irish Sea as well as legal challenges taken.
Speaking in the House of Commons on Thursday, Sir Jeffrey urged the Government to fulfil commitments in the Acts of Union 1800 as it “created the United Kingdom for the people I represent” and entitles everyone to the same privileges – including on trade.
The DUP leader said future arrangements must “avoid any diversion of trade”, adding: “It is simply unacceptable that businesses and consumers in Northern Ireland are told that they must purchase certain goods from the EU and not from Great Britain.”
Another demand was there should be “no border in the Irish Sea” between Great Britain and Northern Ireland, with Sir Jeffrey adding: “Northern Ireland’s place in the UK internal market must be fully restored.”
The seven tests also include Northern Ireland citizens having a role in any new regulations which impact them, no new regulatory barriers between Great Britain and Northern Ireland unless agreed by the Stormont Assembly as well as honouring the “letter and spirit” of the region’s constitutional position as set out in the Good Friday Agreement by requiring upfront consent of any diminution in constitutional status.
Sir Jeffrey emphasised these tests are grounded not in a “unionist wish list, but in promises that have already been made in one form or another, to the people of Northern Ireland”.
“I do not believe that it is too much to ask that the Government stands over these promises,” he added.
“There is no practical or pragmatic reason why arrangements cannot be put in place which can satisfy these tests and prove no meaningful threat to the integrity of the EU Single Market. But with or without the agreement of the EU it is critical that the UK Government honours the promises that have been made to the people of Northern Ireland.
“My party will be assessing any new arrangements against these seven tests and I hope for the sake of the integrity of the United Kingdom and the people of Northern Ireland, we will not be disappointed.”