"Ian has obviously lost credibility," Lord Trimble told the Belf ast Telegraph in his first in-depth interview since this week's announcement that the First Minister is stepping down after just one year in office.

He added: "I'm not surprised. It was obvious at the last General Election (in 2005) that DUP were not being, shall we say, transparent in their canvass.

"I told people on the doorstep that Ian Paisley was about to do a deal with Sinn Fein - a deal that would be the identical twin of the Good Friday Agreement.

"His supporters said he would never do that, but my predictions came true in a very short time, and the 'Chuckle Brothers' images of Ian Paisley and Martin McGuinness are the outworkings of that."

When asked had Dr Paisley been on an 'ego trip' as First Minister - in that it was felt he had to lead every organisation he joined, like the Free Presbyterian Church and the DUP - Mr Trimble replied: "I simply don't know. You'd have to ask Ian Paisley that.

"But the fact that he was summarily removed as Moderator of the Free Presbyterians, and that the pragmatists wanted him out as party leader and First Minister show his actions since his about-turn have not gone down well.

"I feel that his failure to explain his change of heart to his supporters hastened his demise.

"In normal circumstances, I feel the time was fast approaching for him to step down, anyway - perhaps age, perhaps he was an opposition politician, rather than a hands-on ruling politician."

Lord Trimble said that all the discontent was crystallised in the recent Dromore by-election result where the intervention of Jim Allister's Traditional Ulster Voice (TUV) grouping combined with the UUP to deny the Paisleyites their expected victory.

"The bottom line is the Ulster Unionists won that seat," said Lord Trimble. "People knew that we had been honest with them all along. DUP weren't, and ended up settling on a deal that was a mirror image of the Belfast Agreement. People aren't fools. The pragmatists in DUP realised that fact, so Ian Paisley had to go."

He insisted, though, that the Allister element would not amount to much in Ulster politics.

"Jim Allister doesn't have a viable alternative strategy for Northern Ireland," he claimed. "Peter Robinson - or whoever takes over from Ian Paisley - will continue to work with Sinn Fein. I always said the two parties would find a lot in common.

"But it won't be so upfront. It will be business-like, without the 'Chuckle Brothers' element."

He added: "This is, of course, a golden opportunity for a renaissance of the UUP.

"We were honest and open with the electorate. DUP were not, and I believe that will be reflected in future elections.

"The Good Friday Agreement removed the Constitution fears from the political process, and the violence has ended.

"Normal politics will slowly evolve, and in that context, Ian Paisley's ways are in the past."

On the Ian Paisley jnr influence on the overall scenario, Lord Trimble said he did not want to comment in any great depth.

"Ian Junior's actions were something of a sideshow," he stated. " I don't think they affected the overall political scene."

He insisted he did not feel bitter over the events of the past decade - from 1998 when Ian Paisley and his followers shouted at the gate when the Good Friday Agreement was being negotiated, "and when Tony Blair made promises that he never kept, that Paisley and DUP would be sidelined".

"I can honestly say that the deal we struck has now stuck," he reflected.

"And if Tony Blair didn't topple Ian Paisley, then his own party colleagues did it.

"The pity is that it took so long for the Good Friday Agreement - aka the St Andrews Agreement - to take hold.

"Meanwhile, I have moved on and am enjoying my role in the House of Lords, and as a sort of emissary for the Conservative Party."

He concluded: "It has to be said that Ian Paisley has had quite an influence in Northern Ireland politics over the past four decades - from the 'O'Neill Must Go' phase to the 'Trimble Out' era.

"Most of it, however, has been negative, and when he was called upon to be positive, he failed to measure up.

"It's one thing shouting from the political sideslines - it's quite another thing actually governing a country.

"I lasted four years as First Minister. He lasted one.

"And I would ask a final question - would Terence O'Neill have shared power with the IRA while he was Prime Minister of Northern Ireland?

"I leave that one hanging in the air..."