'It could be game over for the Union': TUV leader Jim Allister gives verdict on DUP agreeing deal with UK government on post-Brexit trade arrangements

He said he believed the deal would mean that Northern Ireland “will never again be a full part of the United Kingdom”.

“That, of course, is to our detriment because it puts us on transition out of the United Kingdom through the application of the common laws that apply north and south into an evolving all-Ireland economy. That’s something that no unionist leader should be doing and certainly shouldn’t be dressing it up as something else.”

He added: “It could be game over for the Union, because he’s (DUP leader Sir Jeffrey Donaldson) accepting that never again will we be a full part of the United Kingdom. He’s accepting that we will be ruled by foreign laws. He’s accepting an Irish Sea border. He’s accepting that GB in terms of the EU customs code is a foreign country.

“Those are astounding concessions for any unionist leader to make and they’re bound to have constitutional repercussions.”

‘Tawdry climbdown’

Mr Allister said the DUP’s decision represents a “tawdry climbdown” which is of “significant and adverse constitutional consequences”.

He said the deal would see Northern Ireland become a “condominium ruled in part by UK laws and ruled in part by EU laws”.

“We’re left in the situation where as far as the laws that govern our goods economy, which is a vital part, as far as those laws are concerned, they are not the laws that prevail in the rest of the UK, they are identical to the laws that prevail in the Irish republic,” he said at Stormont.

“So, by that means, the transition of an all-island economy remain secured under the protocol.

“And, of course, the manifestation of the fact that we’re under the EU customs code with GB to create a foreign country in terms of trade, and the fact that we’re under EU law manifests itself in the Irish Sea border, which continues.

“So, when you take those facts, those unalterable facts and those facts unaltered by the DUP deal, then it is quite clear that our place has not been restored within the United Kingdom and all that we have here as a tawdry climbdown by the DUP on their own tests, which patently have not been met.”