Sinn Fein could face increasing pressure to dump its abstentionist policy at Westminster if Labour narrows the gap on Conservatives in the General Election, it has been claimed.
Republicans insist their historic boycott of the House of Commons is not changing, despite polls showing Labour advances.
Sinn Fein Stormont leader Michelle O'Neill said: "We represent people at Westminster where our full-time MPs punch way above their weight.
"We refuse to give any credibility that a handful of MPs sitting in Westminster can have a real impact in the British Parliament."
Her comments came as an increasing number of polls indicate Theresa May's government may not have the landslide Conservative majority she asked for to give her a "strong hand" in negotiations over Brexit.
DUP deputy leader Nigel Dodds dismissed the polls, which have been increasingly called into question following the Brexit verdict a year ago and the election of US President Donald Trump.
"We are looking at these polls with a great pinch of salt," Mr Dodds said.
"The only poll which counts is that which takes place on election day next week."
Referring to Sinn Fein's absentionist policy, he added that those who had written off any prospect of Northern Ireland MPs having significant influence in the next British parliament "need to be very careful" - because those who did not turn up will "have no influence whatsoever".