A DUP MP has suggested his party will not back the Tory government in the Commons if it 'caves in' to "unreasonable" demands from Brussels over a Brexit deal.
The party agreed a 'confidence and supply' deal with the Tories after last year's general election. The agreement effectively props up Prime Minister Theresa May's minority government.
However, the DUP failed to back the government on Wednesday night by abstaining from voting on a Labour amendment to an Agriculture Bill outlining post-Brexit reforms. Despite their abstention, it was still defeated by 59 votes.
East Antrim MP Sammy Wilson said the party's abstention acted as a "warning" to the government.
The DUP previously said it may refuse to back the budget later this month.
Conservative MP Helen Grant said she believed the north's largest unionist party was "bluffing" about withholding its support.
However, Mr Wilson said the DUP was unhappy that "briefings and leaks" suggested the British government may consider excluding the north from the UK's trade deals or agree to checks on goods arriving from Britain.
"It was a way of reminding the government that while our vote wasn't important last night, it would be important some time in the future, and we would have no hesitation withholding it if we thought that was a necessary sanction to impose," he told the BBC.
"It was a warning: 'Don't take us for granted, we're in an agreement with you, but it's a two-sided agreement."
He added: "If they (the government) decide to cave in to the unreasonable and unnecessary demands which are being promoted by Brussels, then we will have to consider whether or not they have kept their side of the bargain.
"If they haven't, there'll be consequences, and one of the consequences is the votes that we have promised to deliver for their domestic legislation will not be forthcoming."
Mr Wilson said if the British government were to accept the EU's current proposals for a 'backstop' - an Irish government plan to prevent a hard border - the DUP may refuse to back the next budget.
He said Mr Barnier's demands included "that we would stay as part of the single market, our laws in NI would be made in Brussels, not London, that we would not be able to be part of future UK trade deals, that the ECJ would make decisions about the rules and regulations in Northern Ireland".
