DUP leader Arlene Foster said the Conservative Party’s loss in the Brecon and Radnorshire by-election does not affect her party's pledge to support the government.
Boris Johnson has been left with a one seat majority in the House of Commons after the Welsh by-election, propped up by the backing of 10 DUP MPs.
Ms Foster told talkRADIO’s Julia Hartley-Brewer that the victory of the Liberal Democrats “doesn’t change things".
“The confidence and supply agreement which we signed with the Conservative Party after Theresa May became the Prime Minister still remains,” she said.
“The nation needs stability at this time as we go through what are history-making times. So it’s very important for us that Parliament respects the wishes of the people clearly expressed in June of 2016.”
Liberal Democrat Jane Dodds won by 1,425 votes, defeating former Tory MP Chris Davies who was forced to step down from the seat over an expenses scandal.
Ms Foster said she was alarmed Ms Dodds pledged to “beat Brexit” in her victory speech.
“I think one of the most striking things of the new MP last night was that the first thing she wanted to say was that she was going to disrespect the wishes of the British people and stop Brexit, which I think is very striking indeed,” she said.
She said the combined support for the Tories, Brexit Party and UKIP showed there was “still a leave majority” in Brecon and Radnorshire.
The DUP leader said she wants to avoid a no-deal Brexit but was pleased to see Mr Johnson’s government planning for the possibility.
“It is important that the government puts interventions in place to mitigate against all of these matters and I much prefer the approach of the new Chancellor and of the government in being prepared,” she said.