DUP warns it could bring down government if Northern Ireland kept in customs union

Theresa May's DUP allies have threatened to bring down the Government if Northern Ireland is kept inside the EU’s customs union after Brexit.

Nigel Dodds, who leads the DUP at Westminster, said he would be willing to ditch his party’s confidence-and-supply agreement with the Conservatives if the province was forced to remain part of the tariff-free zone as part of the final Brexit deal.

Britain has agreed to Brussels' so-called "backstop" demand that Northern Ireland should stay in the customs union and parts of the single market if no other mechanism is found that would avoid a hard border with the Republic.

Asked by Conservative Home what might lead to the DUP removing its support for the Government, Mr Dodds said continued membership of the customs union would “cross a very big red line for” for his crucial bloc of 10 MPs.

He said: “For us there is the fact that if as a result of the Brexit negotiations for instance there was to be any suggestion that Northern Ireland would be treated differently, in a way for instance that we were part of a customs union and a single market and the rest of the UK wasn’t.

"If there was anything like the EU’s definition of the backstop arrangements that was agreed in December – for us that would be a red line, which we would vote against the Government, because you might as well have a Corbyn government pursuing openly its anti-unionist policies as have a Conservative Government doing it by a different means.

Supporters of the customs union argue that it is the best way to maintain an open border between Ireland and Northern Ireland, but the DUP is firmly against any plan that would see Northern Ireland subject to different post-Brexit arrangements from the rest of the UK.

While Mr Dodds said he had “no reason” to believe May - who has repeatedly ruled out customs union membership - would keep Northern Ireland in the bloc, he warned that the DUP would not countenance any suggestion “that Northern Ireland were to be treated differently, in a way that Northern Ireland didn’t agree to”.

The DUP heavyweight’s remarks come ahead of what is set to be a heated House of Commons debate on the customs union later today, with senior Tories including Nicky Morgan, Bob Neill, Sarah Wollaston and Dominic Grieve set to call on ministers to back "the establishment of an effective customs union” between the UK and the EU after Brexit.

Downing Street has dismissed the non-binding vote, which could gauge the size of any future rebellion over the issue, as a “routine backbench business debate".

Meanwhile, The Sun reports that May is set to publish a 50-page document of demands for a post-Brexit trade deal with the EU in a bid to set the agenda in talks with Brussels and shore up support from Conservative backbenchers.

The strategy - agreed at yesterday’s meeting of the government’s so-called Brexit ‘war cabinet’ - will include a list of demands on areas including security and trade, and could be published as early as next month.

A Whitehall source told the paper: “We have learned from the EU’s tactics of the last two rounds. We are not going to wait for Michel Barnier to box us in again. The PM wants us to set the agenda now, and the pace too.”