Former British prime minister John Major has said he is concerned about a planned deal between Prime Minister Theresa May and the Democratic Unionist Party to shore up Mrs May's minority government.
"I am concerned about the deal. I am wary about it. I am dubious about it," Mr Major told BBC radio.
He said he was worried principally that the planned agreement could hurt the Northern Irish peace process in which the British government plays an impartial role.
However, this evening Mrs May said her party was "absolutely steadfast" in its commitment to the peace process.
Meanwhile Martin Mansergh, a negotiator of the Good Friday Agreement, said the DUP could do a great service not just to Northern Ireland but to the whole island, if they throw their weight behind Britain staying in the customs union.
Speaking on RTÉ's News at One the former Fianna Fáil minister said this would "solve most problems related to the border".
Mr Mansergh said whilst the DUP said they do not want a hard border, they have not said they want a soft Brexit.
He said people have to be "vigilant" that the talks in Westminster remain separate from the talks at Stormont.
Earlier, the European Parliament's chief Brexit negotiator said ensuring that there is no hard border and that there is respect for the Good Friday Agreement is "more of a priority" after the UK election result than it has been previously.
Speaking to journalists in Strasbourg, Guy Verhofstadt said the Good Friday Agreement has to be a priority.
He said: "We need to avoid a hard border between Northern Ireland and the Republic of Ireland. This is more of a priority since the Tory government is looking to secure a deal with the DUP.
"Respect for the Good Friday Agreement and the need [to] avoid a return to a hard border is more of a priority than it was in the previous weeks and months."
He said that Europe is still waiting on the UK to decide its position on Brexit.
The former Belgian prime minister and leader of the Alliance of Liberals and Democrats (ALDE) group added: "It's unclear if the UK government will stick to the line that they had announced in their March 29 letter or if they will change it, taking into account the outcome of the election."
He said the EU has always welcomed a close relationship with the UK. "We preferred a Norwegian style relationship or a customs union."
But he said the EU will never compromise in the Brexit negotiations on a number of conditions, including a fair financial settlement and an effective legal framework.
Mrs May is facing growing pressure to pursue a more cross-party approach to Brexit with greater focus on the economy amid reports of secret talks between cabinet ministers and Labour MPs.
Scottish Conservatives' leader Ruth Davidson, whose influence has grown dramatically with the election of 13 Tories north of the border, has already broken cover to say "this isn't just going to be a Tory Brexit".
Mrs May's weakened position in the House of Commons as a result of losing her majority has fuelled speculation the Tories would be forced to soften their stance on Brexit.
A number of British newspapers have reported that cabinet ministers have initiated talks with Labour MPs to secure cross-party backing for a softer Brexit.
Ms Davidson has suggested the government may shift its priority from cutting immigration to ensuring a good deal for business and the economy.
After Mrs May addressed the 1922 Committee of backbench Tory MPs yesterday, some of those present suggested the prime minister would consult more with business on her approach to the talks.
Ms Davidson said: "We do have to make sure that we invite other people in now. This isn't just going to be a Tory Brexit, this is going to have to involve the whole country.
"We can make a big, bold offer that brings the country with us, that brings people in from the other side of the aisle in the House of Commons but also brings people in from outside the Commons too."
It comes after Brexit Secretary David Davis revealed that discussions on the UK's exit from the European Union may start later than the previously anticipated date of 19 June.
It came as the European Commission's chief negotiator warned that Britain risks crashing out of the EU with no deal if it wastes any more of the time available for Brexit negotiations.
Michel Barnier urged Mrs May to "very quickly" start talks and appoint a negotiating team that is "stable, accountable and with a mandate" with the clock ticking to 29 March 2019, when the UK is expected to leave after the two-year Article 50 process.
"Next week, it will be three months after the sending of the Article 50 letter," Mr Barnier told the Financial Times and a group of European newspapers.
"We haven't negotiated, we haven't progressed.
"Thus we must begin this negotiation.
We are ready as soon as the UK itself is ready
He added: "Time is passing. It is passing quicker than anyone believes because the subjects we have to deal with are extraordinarily complex.
"It will take months to draw out the conditions of an orderly withdrawal. Let's not waste time."