The "hatred" the DUP had for the PUP was evident in an encounter Ian Paisley had with Billy Hutchinson while both were Assembly MLAs, the leading loyalist reveals.
In his new biography, released this weekend, Hutchinson tells how the pair were involved in a tense stand-off in an elevator at Stormont, trading insults.
Hutchinson explains: "One day I was getting into the lift and suddenly heard heavy footsteps hurrying along the corridor. 'Stop the lift, please!' The thundering tone and the Ballymena accent were unmistakable.
"I held the button to keep the doors open. As a breathless Paisley went to step into the lift, he looked up and realised that I was inside it. 'Go on!' he panted, 'I'll not be getting in a lift with a UVF murderer!'
"There was an awkward pause for a second before I responded: 'Well, it didn't worry you too much when you sent Tom McDowell to his death'."
McDowell was a loyalist bomber who died after electrocuting himself while trying to bomb an electricity switching station in Ballyshannon, Co Donegal, in 1969. There have been claims that the attack was funded by Ian Paisley. Last year the BBC series, Spotlight On The Troubles: A Secret History interviewed former British army officer David Hancock, who said an RUC district inspector in Kilkeel, informed him Paisley had supplied money for a number of bombings of water and electricity installations by the UVF and the Ulster Protestant Volunteers.
Hutchinson said: "As the doors to the lift slowly closed, Paisley's face dropped and for once he was speechless. Here was a man who had led the loyalist people to heartache and death, and still, thirty years later, he hadn't changed his tune. He was a total hypocrite.
"The DUP seemed to hate us even more than Sinn Féin. They called us Mo Mowlam's pups in what was a crass attempt to make the loyalist people think that we were merely the secretary of state's playthings.
"They were afraid that we were edging in on their vote."
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Billy Hutchinson is talking about murder. He was just 18 years old when he drove the car used in the double killing of half-brothers Michael Loughran and Edward Morgan.