DUP kingmakers threaten to pull support for Britain's May

Northern Irelands Democratic Unionist Party on Thursday threatened to withdraw its support for British Prime Minister Theresa May if she compromises with Brussels in a move that could bring down the government and trigger an election.

Writing in the Daily Telegraph, DUP Brexit spokesman Sammy Wilson warned that any checks on goods transiting between Great Britain and Northern Ireland of the type outlined by EU negotiator Michel Barnier on Wednesday would be "unacceptable".

If the DUP votes against the budget, which is due to be presented to parliament on October 29, this could trigger a confidence motion and an election if the government loses.

Accepting the demands from Brussels "would have implications not just for Brexit legislation -- 50 percent of which would not have passed without DUP support -- but also for the budget, welfare reform and other domestic legislation", Wilson wrote.

"As a unionist party, we will not give our support to any deal that includes such economically and constitutionally damaging arrangements," he said, warning that the party would hold firm even if the government tries to "bribe, bully or browbeat us".

In what was interpreted as a warning shot against the government, DUP lawmakers on Wednesday failed to back the government in voting against an amendment to an Agriculture Bill.

'Stifling embrace of the EU'

The main sticking point in Brexit talks is agreeing on a legally binding "backstop" arrangement to keep open the border between British-ruled Northern Ireland and the Republic of Ireland, an EU member state, whatever the outcome of future trade talks.

Barnier said on Wednesday that "administrative procedures" would be required on goods travelling to Northern Ireland from the rest of the UK if the border is to remain free-flowing.

European Union proposals would keep Northern Ireland in its customs union and force the province to abide by European single market rules.

May has insisted she will not accept any deal that creates "a border down the Irish Sea" but recent reports have indicated that her government may be willing to compromise.

May is due to hold talks with key ministers about the current state of Brexit negotiations later on Thursday ahead of a crunch summit next week with EU leaders.

"To date the government has signalled to the EU negotiators that we are a soft touch who can be pushed around," Wilson said.

"As a result, we have encouraged the EU to stick to its unrealistic demands that internal economic and regulatory boundaries be imposed within the UK," he said.

He said Northern Ireland did not want to be left "languishing in the stifling embrace of the EU" and warned that the province could "forever be stuck in the customs union".