Ulster Unionist leader Robin Swann has dismissed Sinn Fein's call for a border poll as an attempt to distract attention from the party's failure to broker a deal to restore power-sharing.
Sinn Fein repeated its demand yesterday after meeting Secretary of State Karen Bradley in London and claimed the Government was "in disarray" over the issue.
Mrs Bradley has said there is no prospect of a poll in the foreseeable future as the majority of people are happy to stay in the UK.
It was reported earlier this week that Prime Minister Theresa May was not confident the Government would win a referendum on the issue.
Mr Swann said: "The current noise coming from Sinn Fein over a referendum on Northern Ireland's future is nothing more than a distraction.
"They'll do anything but talk about their total abdication of responsibility to the people of Northern Ireland.
"This latest campaign demonstrates that they place ideology ahead of the needs of ordinary people.
"It is totally laughable that they are pursuing a border poll at a time when they won't even take their seats in the devolved institutions.
"Our health service is at breaking point and people are languishing on waiting lists because no strategic decisions can be made. Is this a vision of what could be expected in a united Ireland?"
Mr Swann said Sinn Fein's claim that other parties were attempting to subvert the Good Friday Agreement showed the party was "on another planet".
He said: "They are only interested in the Belfast Agreement when they think it can be used as a tool to progress their own party political interests.
"They have spent the last 20 years skipping past the part on the principle of consent.
"If only they pursued providing Northern Ireland with effective and accountable governance with the fervour they do a border poll we wouldn't be in the state of paralysis we find ourselves," he added.
Speaking after meeting Mrs Bradley, Sinn Fein MP Elisha McCallion said her party had challenged the Government over Mrs May's reported comments about opposing a border poll because she believed unionists could lose.
Ms McCallion said: "Effectively, the British Prime Minister was conceding that the Good Friday Agreement threshold for triggering a unity poll has been met but she isn't prepared to allow the people of Ireland, North and South, to exercise their democratic right.
"That is an appalling display of contempt for the democratic rights of Irish citizens and today Karen Bradley again claimed that the threshold for a unity referendum has not been met.
"So she is saying one thing and Theresa May is saying another. This is just another example of the clear disarray within this Tory government."
Ms McCallion continued: "On five occasions now Sinn Fein has asked the British Secretary of State to set out the criteria whereby they come to the conclusion that the threshold has not been met.
"They have yet to produce a shred of documentation to justify this decision. That simply isn't good enough. They are undermining the Good Friday Agreement and denying democratic rights to Irish citizens without any justification whatsoever."
SDLP MLA Justin McNulty said any future border poll shouldn't be treated "as a race to the finish line" by nationalists but rather as "an opportunity to sell a new Ireland to the unionist community".
He said: "Despite the Prime Minister's comment that she believes unionists would not be guaranteed a win in a border poll, it is imperative nationalists recognise the body of work that needs to be done to ensure its success and sustainability."
Any new Ireland must be fully inclusive of unionists' identity, the SDLP MLA stressed.
"Persuasion, honesty and creativity will be required moving forward with this discussion," he added.
The Times reported an alleged confrontation between Mrs May and MP Jacob Rees-Mogg over a border poll. Sources said the backbencher told her that he had "no doubt" Northern Ireland would remain within the UK after any referendum.
Apparently Mrs May responded: "I would not be as confident as you. That's not a risk I'm prepared to take."