The Prime Minister is to hold talks with political leaders from Northern Ireland in a bid to allay fears the anticipated parliamentary deal with the Democratic Unionists will undermine the peace process.

Theresa May will mee Sinn Fein, the Ulster Unionists, the SDLP and Alliance Party in separate engagements at Downing Street on Thursday afternoon.

The move comes amid concerns the British government will compromise its stated impartiality in the region if it enters a confidence and supply deal with the DUP at Westminster.

Sir John Major is one of those urging caution.

Sinn Fein, the SDLP and Alliance have all made clear Northern Ireland Secretary James Brokenshire cannot chair the ongoing process to restore powersharing at Stormont due to their perception he has a conflict of interest.

While the DUP continue to hammer out the details of the arrangement with the Tories, the other four main parties at Stormont confirmed they would be meeting Mrs May on Thursday.

The 1998 Good Friday Agreement commits the UK and Irish Governments to demonstrate "rigorous impartiality" in their dealings with the different political traditions in Northern Ireland.

Sinn Fein's Stormont leader Michelle O'Neill said: "I will be making it very clear that any deal between the Tories and the DUP cannot be allowed to undermine the Good Friday and subsequent agreements."

The announcement of any deal between the DUP and Conservatives will likely be delayed because of the tragic fire in a London tower block.

Mrs May needs the votes of the DUP's 10 MPs to prop up her minority administration as she hopes to steer government business, including crucial measures on Brexit, through the Commons.

A Conservative source said there was so far no deal to announce and that a decision on the timing of any announcement would have to wait until an agreement was finalised.

Ministers have already said that the Queen's Speech may have to be set back from its scheduled date of next Monday June 19, because of the ongoing negotiations.

Mrs May is coming under intense pressure to change her approach to leaving the European Union, with predecessor David Cameron among those suggesting a softer stance with a greater effort to seek a consensus.

Talks with the DUP broke up on Tuesday night without an agreement, but Mrs May said the discussions had been "productive".

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".

The proposed deal would see the DUP back the Conservatives in votes on the Budget and confidence motions.

For Labour, shadow business secretary Rebecca Long-Bailey said the prospect of a Conservative-DUP deal was "worrying", telling BBC Radio 4's Today programme: "It would create a lot of instability in terms of the peace process in Northern Ireland."

One of the most pressing issues facing Mrs May is the process of leaving the EU, with Brexit talks set to start in Brussels on Monday.

Former prime minister Mr Cameron said Mrs May would have to change her approach to Brexit as a result of the election.

"It's going to be difficult. There's no doubt about that, but perhaps an opportunity to consult more widely with the other parties on how best we can achieve it," he said at a conference in Poland.

"I think there will be pressure for a softer Brexit," Mr Cameron added, saying that Parliament now "deserves a say" on the issue.

He also suggested the Scottish Tories led by Ruth Davidson could also add to the pressure on Mrs May to change course.

The Times reported that Chancellor Philip Hammond was preparing to fight for the UK to remain within the EU's customs union.

That would help safeguard jobs and trade with EU members, but would severely restrict the UK's ability to strike its own trade deals around the world.

At a joint press conference with Mrs May in Paris on Tuesday night, France's President Emmanuel Macron suggested the door was still open for the UK to remain within the European Union.

"Until the negotiations come to an end, of course there is always the possibility to re-open the door," said Mr Macron.

"But let us be clear and organised and once the negotiations have started we should be well aware that it'll be more difficult to move backwards."

Mrs May stressed Brexit would happen and the timetable remains on course.

She said: "I think there is a unity of purpose among people in the United Kingdom.

"It's a unity of purpose, having voted to leave the EU, that their Government gets on with that and makes a success of it, and we are committed to developing a deep and special partnership with the EU."