Former Labour spin doctor Alastair Campbell has accused Theresa May of threatening the peace process in Northern Ireland by negotiating a "sordid, dangerous and distasteful" deal with the DUP.
Speaking on the BBC's Question Time, he said he was "really, really" worried about the potential deal between the Tories and the Democratic Unionist Party (DUP) after the prime minister failed to get a majority in the election.
Despite many predicting the party would win a majority of as many as 70 seats, Ms May fell eight seats short of a majority with 318 seats.
She has now entered into negotiations with the unionist party, which won 10 seats, to form a "confidence and supply" alliance which would help them pass legislation on a case by case basis.
Mr Campbell accused Ms May of "playing fast and loose, on Brexit, on Margaret Thatcher’s greatest achievement the single market and now Tony Blair and John Major’s greatest achievement which is the peace in Northern Ireland".
He said: "She is putting that at risk with a sordid, dangerous distasteful deal."
There has been no government in Stormont since January when Sinn Fein withdrew from the power sharing agreement agreed in 2007 after current DUP First Minister Arlene Foster refused to resign over a financial scandal.
After assembly elections in March where the nationalist party won its highest ever number of seats they still refused to re-enter a power sharing government with the DUP while Ms Foster remained in her post.
Under the terms of the power sharing agreement, while the DUP leader is First Minister the Sinn Fein leader must be Deputy First Minister.
Some have criticised Ms May is willing to get into bed with the party which is notorious for its anti-LGBT rights, anti-abortion and anti-women policies as well as its alleged links to unionist terrorists.
The Conservatives, whose full formal name is the Conservative and Unionist party, has had long links with unionist parties in Northern Ireland but its former traditional partner in the region – the more moderate Ulster Unionist Party (UUP) – was wiped out.
Mr Campbell has called into question whether the Government can include the DUP without threatening the delicate power sharing agreement between them and Irish nationalists Sinn Fein which has helped end The Troubles.
The newer DUP became the largest unionist party in Northern Ireland in 2005 and Reverend Ian Paisley, the Protestant evangelical minister who founded the party in 1971, became First Minister in 2007.
Mr Campbell, who worked with Tony Blair and Mo Mowlam to get the Good Friday agreement signed, said: "I really, really have a worry about this. When John Major was weak and he could have done a deal with the DUP he absolutely and steadfastly refused to do so for very good reasons.
"He said 'I do not what to be in hoc that government'....We have a situation in the Northern Ireland right now where there has been a political crisis where the Government is the mediator with the Irish government between the DUP and Sinn Fein.
"How can our government be the mediator when the DUP are going to be part of our government?"
He said she was destroying New Labour's legacy of peace in Northern Ireland to prop herself up in government.
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