FILE PHOTO: Democratic Unionist Party (DUP) leader Arlene Foster speaks, at the DUP annual party conference in Belfast, Northern Ireland November 24, 2018. REUTERS/Clodagh Kilcoyne

BELFAST (Reuters) - Northern Ireland’s Democratic Unionist Party, whose 10 votes British Prime Minister Theresa May relies on for a majority in the British parliament, confirmed on Tuesday that it will vote against her proposed Brexit withdrawal deal.

“Tonight will be historic but for the wrong reasons,” DUP leader Arlene Foster said in a post on Twitter ahead of the vote in parliament on the deal. “We will oppose the toxic backstop & vote against the WA,” she said, referring to the Withdrawal Agreement.