THE backstop has gone and the UK-EU deal makes clear that Northern Ireland is “part of the customs territory of the United Kingdom” but the Democratic Unionists believe Boris Johnson’s new withdrawal plan would undermine the Union.

The new deal stresses that as part of the UK's customs territory, Northern Ireland would be included in any future trade deals struck by the Government post Brexit.

Yet, in a practical sense, Northern Ireland will effectively be in the EU’s single market and customs union with a border down the Irish Sea.

The UK will apply tariffs to products entering the province as long as they are destined for onward transportation across the border into the EU.

A new joint UK/EU committee will determine which goods are en route to enter the single market and the UK would collect EU tariffs on them on behalf of Brussels.

Every four years, Stormont - which has been suspended since January 2017 - would get a vote to decide on whether or not it wanted to continue with the new trading arrangement.

But the decision would be based not on a requirement for a majority among both the Unionists and the Nationalists but by a simple majority, thus removing an effective DUP veto.

The party issued a statement, making clear it could not support the Prime Minister's plan.

It declared: "These proposals are not beneficial to the economic well-being of Northern Ireland and they undermine the integrity of the Union.”

The DUP explained: “Our main route of trade on an East-West basis will be subject to rules of the European Union Customs Union, notwithstanding that Northern Ireland will remain part of the UK Customs territory.

"All goods would be subject to a customs check regime regardless of their final destination. The default position, even for goods travelling from one part of our country to another, is that they are considered under the EU Customs code unless otherwise agreed.

"We recognise that only those goods ultimately destined for the Republic of Ireland would be subject to tariffs but the reality remains that the EU would have a veto on which goods would be exempt and which would not under the Joint Committee arrangements. This is not acceptable within the internal borders of the United Kingdom."

The statement noted how consumers in Northern Ireland would face increased costs, and potentially less choice due to checks being implemented in order to facilitate the EU. It said on VAT the province would again be bound into arrangements that the rest of the UK would not be.

“There is a real danger that over time Northern Ireland will start to diverge across VAT and customs and without broad support from the democratic representatives of the people of Northern Ireland.

"While some progress has been made in recognising the issue of consent, the elected representatives of Northern Ireland will have no say on whether Northern Ireland should enter these arrangements.”

The DUP said the Government had departed from the principle that these arrangements must be subjected to the consent of both Unionists and Nationalists in Northern Ireland.

“These arrangements would be subject to a rolling review but again the principles of the Belfast Agreement on consent have been abandoned in favour of majority rule on this single issue alone.

"These arrangements will become the settled position in these areas for Northern Ireland. This drives a coach and horses through the professed sanctity of the Belfast Agreement,” it declared.

The party added: "For all of these reasons it is our view that these arrangements would not be in Northern Ireland's long term interests. Saturday's vote in Parliament on the proposals will only be the start of a long process to get any Withdrawal Agreement Bill through the House of Commons."