The Democratic Unionist Party, whose controversial policies include blocking gay marriage, could hold the balance of power in the new Parliament.
The Northern Irish party looks likely to give the Conservatives its support to form a government.
If it manages to become part of the government and hold it up, however, it may be able to introduce the kinds of policies that have become controversial in Northern Ireland.
That has included moves by the party to oppose the introduction of same sex marriage in Northern Ireland, as well as lifting the ban on abortion. Those laws have been in place across the rest of the UK, but the DUP has helped block them in Northern Ireland in recent years.
Leader Arlene Foster all but confirmed that the DUP would never join a coalition with Labour. She said that she had “always said” the party would find it hard to work with Jeremy Corbyn.
The party, alongside Sinn Fein, has made strong gains in the election at the expense of the Social Democratic and Labour Party (SDLP) and the Alliance Party.
The DUP replaced the SDLP in South Belfast, wrested back South Antrim from the Ulster Unionist Party and saw off the challenge of the Alliance Party and Sinn Fein in East and North Belfast respectively.
With speculation the DUP could hold an influential position in Westminster, party leader Arlene Foster declared it a “good night for the Union”.
She said: “We’ll wait to hear what the results actually are, but we are very pleased with the way in which people have reacted to the positive message of the campaign – it was about the Union, the importance of the Union, and unionists have really come out in their numbers.
“We fought this election on the importance of the Union and I think people really responded to that.”
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