THERESA May is on the verge of clinching a deal with the Democratic Unionists that will keep the Conservatives in power as Sir John Major warned the move risked endangering Northern Ireland’s “fragile” peace process.

Speaking after hours of talks between the two parties, Arlene Foster, the DUP leader, made clear Brexit, counter-terrorism and "doing what's right" for the Northern Irish economy were among the key issues being thrashed out.

She said the discussions were going well and she hoped to bring them to a successful conclusion "soon." The former Stormont First Minister had planned to return to Belfast last night but cancelled her flight, which points to a possible announcement in Whitehall later today.

Discussions at Westminster continued without the Prime Minister, who left for France for a pre-arranged meeting with Emmanuel Macron, the newly-elected President.

In Paris, Mrs May said last week’s General Election had revealed "a unity of purpose" among British voters for the Government to get on with Brexit and she confirmed the withdrawal talks would start next week as planned.

In an unexpected move, Mr Macron said that the EU “door remains open, always open[to Britain], until the Brexit negotiations come to an end”.

The remarks suggested that the French President not only believed that Britain could change its mind on leaving the EU but also that the UK Government’s minority status meant there was a reduced mandate for Brexit in Britain.

Earlier, the PM appointed Steve Baker, the hardline Leaver, as a Brexit minister, who said Britain should seek the “softest” of EU withdrawals while enabling the country to control its own laws, money, borders and trade.

In London, the Tories and the DUP are trying to agree a so-called "confidence and supply" arrangement, which would see the Northern Irish party back the Government to get key votes through such as on its Budget.

The talks come after Mrs May told Tory MPs on Monday night: "I'm the person who got us into this mess and I'm the one who will get us out."

A failure to gain support from the DUP would risk the Queen's Speech being voted down with the prospect of either Jeremy Corbyn seeking to form a minority government or the country facing another election.

Damian Green, the first secretary of state, has confirmed the Queen's Speech setting out the Government's programme, due on Monday, could be delayed if a deal is not reached in time.

The prospect of a DUP deal was discussed at the first post-election cabinet yesterday. Government sources made clear they were very confident of an agreement being reached, which would give Mrs May a small working Commons majority. “A deal will be done,” insisted one minister confidently.

But Sir John said he was "concerned" about the impact any agreement between the DUP and the Conservatives might have on Northern Ireland’s peace process, warning it could mean the Government would no longer be regarded as impartial.

Noting how the peace process was very hard-earned over very many years, he said: “People shouldn't regard it as a given; it isn't certain, it is under stress, it is fragile.”

He made clear he did not expect the peace process to collapse suddenly because there was a broad consensus for it to continue but he cautioned that politicians had to take care that nothing was done to exaggerate the underlying differences that still existed in the Northern Ireland community.

Sir John said he was "concerned" about the deal between the two parties, explaining how he was "wary" and "dubious" about it "both for peace process reasons but also for others reasons as well".

The former party leader stressed that it was "very important" for there to be an "honest broker" in Northern Ireland and that the "only honest broker can be the UK Government".

He added: "The danger is that however much any government tries they will not be seen to be impartial if they are locked into a parliamentary deal at Westminster with one of the Northern Ireland parties and you never know in what unpredictable way events will turn out and we cannot know if that impartiality is going to be crucial at some stage in the future."

Sinn Fein, which has already complained of the UK Government being “partisan,” claimed the DUP would be betraying the interests of Northern Ireland if it agreed to prop up a Conservative minority government.

Senior representatives from the party visited London yesterday to hold meetings with ministers and to set up their parliamentary office but made clear it would maintain its traditional refusal to take its seats out of opposition to Westminster's jurisdiction in Northern Ireland.

Meantime, Mr Corbyn claimed Mrs May's premiership had no mandate and no legitimacy and claimed Labour was “now a government in waiting".

Last night, the party leader was greeted with cheers and a 45-second standing ovation as he arrived at the first meeting of the Parliamentary Labour Party in the Commons since the election.

The scenes were in marked contrast to the difficult meetings Mr Corbyn had with his critics in the parliamentary party before the election.

He told the MPs and peers: "We must remain in permanent campaign mode on a general election footing. We achieved what we did last Thursday because we were a united party during the campaign and we need to maintain that unity and collective discipline in the weeks and months ahead.”