LONDON (Reuters) – The Northern Irish party propping up Prime Minister Theresa May’s government will vote against her Brexit divorce deal in a key vote in parliament next week, according to one its MPs.

The Democratic Unionist Party are unhappy with the divorce deal’s so-called backstop provision which will align Northern Ireland more closely with the European Union than the rest of the United Kingdom if no other way can be found to avoid a hard border with the Republic of Ireland.

“My party will be opposing this agreement as put forward on the basis that we believe it has left Northern Ireland in a constitutionally vulnerable position irrespective of the assurances that we have been given,” Paul Girvan told parliament in a debate on the deal.