Deputy leader Nigel Dodds and fellow Westminster DUP MPs speaking in Victoria Gardens, central London on Brexit last week. Photo: Jonathan Brady/PA Wire

The North Antrim MP’s comments last night came against a backdrop of diplomatic dispute between London and Dublin over whether Friday’s agreement is even enforceable or merely “a statement of intent” in the words of Brexit Secretary David Davis.

The Irish Government’s unbridled public joy at Friday’s agreement – which it said had “achieved all our goals” – was in contrast to DUP leader Arlene Foster, whose initial response was to say that “there are still matters we would have liked to see clarified; we ran out of time essentially”.

However, in a statement last night, Mr Paisley hailed the deal signed after Friday’s last-minute lifting of the DUP’s veto on an agreement.

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The son of the DUP founder said that as a result of what had been agreed, Northern Ireland “has not been designated some purgatorial relationship of neither being in our outside the EU but will be treated completely the same as every other component part of the UK”.

And, rounding on the Taoiseach, Mr Paisley said that at the start of the week Mr Varadkar “had a ball at his toe and believed he was about to pull off a major coup of having secured Northern Ireland harmonised with the Republic of Ireland”.

Mr Paisley said: “Frankly, whatever efforts are made to characterise this week Leo Varadkar was done over by the EU, the UK and the DUP.”

In further evidence of how the Brexit debate has poisoned what for several years have been positive and pragmatic relations between Dublin and the DUP, Mr Paisley went on: “For weeks I and my colleagues had been warning Dublin that they had overstretched themselves and were attempting to use the Brexit negotiations to undermine Northern Ireland’s place in the UK.

“They were warned that the effort to make the border the centrepiece of the negotiations was misguided and that any discussion about the border was irrelevant until after the trade relationship part of the negotiations had been established.

“Friday’s agreement effectively conceded that point and has relegated the completion of any negotiation about the border to be concluded at the end of the negotiations. Once again a very clear indication that Leo Varadkar has been done over.”

Mr Paisley went on to bullishly talk about the possibility of the UK quitting the EU without a final agreement, meaning that businesses would trade under World Trade Organisation (WTO) rules and tariffs, something he said should “put the fear of the Almighty into the Republic”.

He said that although last week’s agreement to move on to trade talks with the EU was “imperfect”, it had “opened the Brexit negotiations into the important chapter of trade”.

He added “failure to reach an overall agreement means we will end up trading on world trade terms, and whilst that poses significant challenges for some sectors such as agri-food exports for Northern Ireland we would be in most cases isolated from the worst of that consequence as most of our export food market is the rest of the UK making all our exports there zero rated”.

He said: “Our manufactured goods abroad would be subjected to trade tariffs of between 2% to 5%.

“However, in these circumstances the economy of the Republic would be crippled. Given that the UK is one of its significant export markets it would be subjected to massive tariffs into its main market.”

Those comments echo something Mr Paisley said last Monday when he appeared on former Ukip leader Nigel Farage’s LBC radio show in London and said: “I’ve got a very, very clear view on this, Nigel – if we don’t leave and we go for WTO. That’s my position, that’s been my position for a long time and that’s where we need to be if this does not work out.”

Fellow DUP MP Sammy Wilson told the BBC’s Sunday Politics the DUP’s main goal was getting a document “which [on Monday] gave little or no recognition to Northern Ireland’s position within the UK and staying in line with the rest of the UK” changed in that regard.

Mr Wilson was also pressed on the widespread view that last week’s deal makes a UK-wide ‘soft Brexit’ more likely.

He said: “I hate these terms ‘soft Brexit’ and ‘hard Brexit’ – you either leave the EU or you don’t leave the EU.

“I’m still convinced the government, because of the commitments that it’s made, and indeed because of the commitments which other parties have made to their supporters... that we won’t be in the customs union and we wont be in the single market. You can call that what you want.”