DUP efforts to bind the UUP to the Hillsborough Castle Agreement have been derided as “bizarre” by the UUP leader.
Sir Reg Empey's comments come with a crunch Assembly vote on the devolution of policing and justice powers a week away.
The DUP has insisted that it will not endorse the plan — which it negotiated at Hillsborough — without the UUP also on board.
Sir Reg yesterday suggested this stance may be linked to internal discord within the DUP prior to last month's Castle agreement.
He told the Belfast Telegraph: “I think it's the most bizarre situation I've ever heard of — where another political party does a deal, tells us it's a good deal, that they're going to do this with every sinew of their being, but if somebody in another political party doesn't vote for it, they're not doing it.
“It may be their so-called dissident element is looking for cover. It's the most weird set-up that I've ever come across.”
Intensive behind-the-scenes talks are now expected to prevent devolution derailing. DUP deputy leader Nigel Dodds said that a lack of UUP support in the March 9 Assembly vote would be a “serious situation”. He added: “I don't think we would then see progress happening.”
The UUP boycotted last month's unveiling of the Hillsborough Castle Agreement and complained of being excluded from negotiations.
The party has said it will not back the devolution of policing and justice powers unless substantial progress is made on resolving the 11 plus stalemate in education. It is also seeking progress on other issues linked to the running of the Executive.
Amid speculation of growing pressure on the UUP, Sir Reg said: “People can phone up and pressurise whatever they like. It doesn't make any difference at the end of the day. It's the people in the party that take the decisions.”
UUP MLA Basil McCrea yesterday said his party was facing “substantial pressure” from “a number of highly placed sources”.
He added: “When the difficulties are explained to them, people understand that the pressure should not be on us, it should be on those who are not delivering what's needed.”
Mr McCrea said he expects a UUP Assembly group meeting on Saturday.
Asked if he was ready to vote for the devolution of policing powers, he said: “As things stand, no. We've made it quite clear we have to see movement on education and on a number of other issues.
“The Executive is dysfunctional. It really does not work. There is no point being up here unless you are going to get politics delivering something for people. At the moment, politics is delivering nothing. We expect movement. If we do not get movement, we will not be putting our hands up.”