Sinn Fein has decided the time for devolution is over in Northern Ireland, DUP MP Nigel Dodds has said.
The Belfast North MP added that Sinn Fein's "main ambitions lie southwards" amidst fresh talk of a united Ireland.
The comments came as shadow Northern Ireland secretary Dave Anderson urged the Government to take a hands-on approach to resolving the current impasse at Stormont, pressing Prime Minister Theresa May to personally intervene.
Mr Dodds said: "Whilst we are determined to create the conditions for devolution and want devolution to work in partnership with Sinn Fein and others, we need a willing partner, who's willing to work realistically within the parameters of a Northern Ireland with devolved government, within the United Kingdom, within the institutions as agreed, and with Brexit a reality.
"Some of us fear that Sinn Fein have now decided that the time for devolution is over, and they're moving on to a different phase where their main ambitions lie southwards."
Mr Dodds accused Sinn Fein of walking away from talks to restore the executive in Northern Ireland.
Northern Ireland Secretary James Brokenshire said: "I believe that a positive outcome is absolutely attainable, and obviously that duty that we all feel in ensuring that we do reach that positive outcome and creating an executive that is delivering for the people of Northern Ireland."
Earlier, Labour's Mr Anderson had urged the UK and Irish governments to do more to end the current deadlock.
He said: "We need direct and continuing intervention from representatives of the Irish government.
"From this House, we must ensure that the hands-off, let them get on with it, it's all done and dusted attitude that prevailed... is ended.
"I believe that now we need the Prime Minister to show greater leadership and encouragement in the process, and show all in Northern Ireland that the Government want to make this work."
He added: "In the background to all this is the worry that any vacuum could be filled by those for whom the bullet is preferred to the ballot box."
Mr Brokenshire said the Irish Government had been "actively involved" in the talks, while the Prime Minister had been "fully engaged in this process - and remains so".
"There is no hands-off role by this Government in relation to Northern Ireland," said Mr Brokenshire.
"We take our responsibilities very seriously in relation to political stability and governance, and fundamentally that sense of devolved government serving the people of Northern Ireland.
"That is profoundly what we want to see restored at the earliest opportunity."
Commenting on a fresh election, Mr Brokenshire said: "Obviously options remain open, but I would say that there is no public appetite, and I don't discern any broader appetite in relation to having an election, given that we only had one just over three weeks ago."