The Democratic Unionist party, which holds the balance of power at Westminster, will use its parliamentary muscle to prevent any special post-Brexit deal for Northern Ireland that could “decouple” the region from the rest of the UK.

Arlene Foster, the DUP leader, said she welcomed assurances from Theresa May that there will be no “internal barriers” between the province and Britain after the UK leaves the EU.



Foster’s 10 MPs keep May and the minority Conservative government in office.



In her speech to the DUP’s annual conference in Belfast on Saturday, Foster expressed confidence that May’s government will not agree to any post-Brexit special status for Northern Ireland.



Q&A Why is Dublin opposed to the idea of a hard border? Show Hide Ireland’s taoiseach, Leo Varadkar, has been much more sceptical than the UK about the potential for avoiding border posts via virtual checks on importers. Whilst agreeing with British ministers and EU negotiators that it is inconceivable for there to be a return to a hard border with the north, Dublin argues that the best way for the UK to achieve this would be by permanently remaining in a customs union with the EU and seeking single market membership like Norway through the European Economic Area. The UK has conceded that some of this will be necessary in its interim phase after Brexit, but hopes clever technological solutions can allow it have looser economic links in the long run. Varadkar is not alone in being sceptical about whether such a cake-and-eat-it customs and trade strategy is viable.

Nor would the DUP accept any special laws in Northern Ireland that “will have to mirror European regulations”.

The Irish government and northern nationalists have demanded that the region be given special status that would keep it part of the single market and/or the customs union.

They have argued that Northern Ireland is a pro-EU region with 56% of the local electorate having voted to remain in Europe in the referendum.

“No such internal barriers will be countenanced and that as we joined the then-European Community as one nation, will leave as one United Kingdom,” Foster told several hundred DUP delegates.



The DUP leader said that while her party wanted a “sensible Brexit”, it would “not support any arrangements that create barriers to trade between Northern Ireland and the rest of the United Kingdom or any suggestion that Northern Ireland, unlike the rest of the UK, will have to mirror European regulations”.



She continued: “The economic reality for our economy is that our most important trading relationship is with the rest of the United Kingdom and we will do nothing that puts that at risk in any way.”



Foster received a rapturous response to her speech in which she said her party’s MPs would fight for the “best deal for Northern Ireland, but we care about vulnerable people in Bristol and Birmingham every bit as much as those in Belfast”.

She said the successful fight by DUP MPs at Westminster to save the triple lock on pensions and the retention of the winter fuel payment proved this.

On the absence of a power-sharing government in Belfast, Foster said she still believed devolution was the best way to govern Northern Ireland.

Commenting on the row over Sinn Féin’s demand for an Irish language act, which that party says is a precondition to entering a new devolved government, Foster stressed that she had no problem with the Irish language, which she said “does not damage to our unionism or the union we cherish”.



On the £1bn-plus aid package the DUP extracted from May as a price for propping up the Tories, Foster said: “Do you remember how some said that the DUP would pursue a narrow agenda in our negotiations? What was secured was for everyone across Northern Ireland.”

Before Foster’s address Sammy Wilson, the DUP MP for East Antrim, raised one of the biggest cheers of the day when he described Ireland’s prime minister, Leo Varadkar, and the Irish foreign minister, Simon Coveney, as a “pair of cowboys”.



The veteran DUP MP was referring to remarks by both Varadkar and Coveney that advocated a special deal for Northern Ireland, which would in effect keep it with one foot inside the EU.



However, there was less jingoism and overt displays of flag-waving patriotism at this year’s DUP conference. Elected representatives from district councillors right up to DUP figures at Westminster declined to speak without permission from the party’s press office about their views on Brexit, the border or other controversies.