Theresa May insisted the Government was "absolutely steadfast" in its commitment to the Northern Irish peace process as she faced questions on whether a DUP-Tory alliance would put fragile agreements at risk.
The UK Prime Minister’s comments came after predecessor Sir John Major warned that an alliance with the DUP at Westminster risked undermining the impartiality of the UK Government as attempts were made to restore the powersharing administration in Stormont.
An agreement between the Tories and DUP is thought to be close, with Mrs May saying the talks had been "productive" and emphasising the need for "stability" in government.
DUP leader Arlene Foster, who travelled to Westminster for talks with the Tories on Tuesday, said she hoped a deal could be reached "sooner rather than later".
Conservative former Prime Minister Sir John, who was crucial in bringing peace to Northern Ireland, raised concerns about the impact of a Tory deal with the DUP.
He told BBC Radio 4’s World at One programme: "The last thing anybody wishes to see is one or other of the communities so aggrieved that the hardmen, who are still there lurking in the corners of the communities, decide that they wish to return to some form of violence."
But speaking during a visit to Paris to meet French president Emmanuel Macron, Mrs May told reporters: "We as Government remain absolutely steadfast in our commitment to the Belfast Agreement and the subsequent agreements and we continue to work with all the parties in Northern Ireland and the Republic of Ireland in ensuring that we can continue to put in place those measures necessary to fulfil those agreements.
"What we are doing in relation to the productive talks that we are holding with the Democratic Unionist Party is ensuring that it is possible to, with their support, give the stability to the UK Government that I think is necessary at this time.
"We stand at a critical time with those Brexit negotiations starting only next week - I think that stability is important.
"We have worked as a party with the DUP before and those are productive talks.
"The intent is to ensure that we have the stability of Government in the national interest."
Before travelling to the French capital, Mrs May had been leading the talks with the DUP.
Mrs Foster arrived in Downing Street with Nigel Dodds at lunchtime for negotiations with the Prime Minister but they decamped to Parliament to allow Mrs May and the DUP’s deputy leader to speak in the Commons.
The DUP leader said: "There’s been a lot of commentary around the issues that we are talking about and it won’t surprise anyone that we are talking about matters that pertain, of course, to the nation generally.
"Bringing stability to the UK government in and around issues around Brexit, obviously around counter-terrorism, and then doing what’s right for Northern Ireland in respect of economic matters."
The Prime Minister did not mention the ongoing deliberations as she addressed MPs but called on Parliament to "come together in a spirit of national unity" to deal with the challenges facing the country.
Labour leader Jeremy Corbyn turned Mrs May’s election slogans against her, claiming a link-up between the Tories and DUP would be a "coalition of chaos".
He said: "I’m sure we all look forward to welcoming the Queen’s Speech just as soon as the coalition of chaos has been negotiated.
"If that’s not possible, the Labour Party stands ready to offer strong and stable leadership in the national interest."
He later told a meeting of his MPs that Mrs May had "no mandate and no legitimacy" and Labour would remain on an election footing in case the Government collapsed.
A failure to gain support from the DUP would risk the Queen’s Speech being voted down next week, and Mr Corbyn has said Labour will be pushing hard for that outcome.