DUBLIN (Reuters) - The Northern Irish party that British Prime Minister Theresa May’s government relies on for support said on Thursday it would consider supporting a vote of no-confidence if May agrees to EU checks on goods entering the region in Brexit talks.

Democratic Unionist Party Brexit spokesman Sammy Wilson told Ireland’s RTE radio the party’s 10 members of parliament would vote against the UK budget and would consider voting no-confidence in May if the British government breaks the DUP’s red lines in Brexit talks.

“If she agrees a deal which breaks her own promises, then I think we have no alternative,” Wilson said when asked if the DUP would vote against the British budget. “In breaking her promises she would be agreeing to break up the United Kingdom,” he said.

The EU’s chief negotiator Michel Barnier on Wednesday said Britain must accept possible checks on goods moving between its mainland and its province of Northern Ireland, saying Brexit would trigger the need for customs, value-added tax and compliance checks with EU standards.

Wilson said such a deal “would in effect have Northern Ireland ruled by the EU rather than London” and would exclude Northern Ireland from future UK trade deals. Barnier’s suggestion was “gratuitous constitutional vandalism” he said.

Wilson said the party would firstly “decide whether or not voting against the budget is the appropriate way of showing our dissatisfaction.”

For the government to fall there would have to be a subsequent vote of no confidence. “What we would do in those circumstances is something we would have to discuss,” he said.

But he said he did not think May necessarily had to make a choice between an exit deal with the European Union and maintaining the support of the DUP.

“I don’t believe that is the choice. I believe that she should be insisting on the kind of deal with the EU that she has been promising to people in the United Kingdom.”

He suggested an alternative compromise would be for the EU to defend its single market by agreeing to virtual checks on goods crossing from Northern Ireland to the Republic of Ireland.