Former Prime Minister Tony Blair was last night accused of being “naive” after hailing Martin McGuinness and Gerry Adams as “big politicians”.

In a TV interview, Mr Blair said he had grown to admire and like the Sinn Fein leaders, claiming they would have “done well” in any political circumstance.

Mr Blair was speaking as his memoirs, A Journey, went on sale.

In the book, Mr Blair admitted he often “stretched the truth past breaking point in order to get agreement” during the peace process.

During the one-hour interview with the BBC’s Andrew Marr, Mr Blair was asked if he came to like Mr Adams and Mr McGuinness.

“I did in the end, yes ... and I think they were big politicians in anyone's language, if you like,” he said.

“I think they would have done well in any set of political |circumstances.”

But his remarks were slammed by the DUP’s Jeffrey Donaldson, who said Mr Blair was “naive”.

“When you have a former British Prime Minister speaking in such endearing terms of politicians like Gerry Adams and Martin McGuinness, I’m sure many of the victims of IRA terrorism will find that hard to swallow,” he said.

“It’s clear from Mr Blair’s book that at times he misled parties during the negotiations, and I think this should inform our view of Mr Blair’s somewhat naive impression of Gerry Adams and Martin McGuinness.

“In describing them as big politicians, I think he forgets too easily that both of them have been involved with a terrorist organisation.”

During last night’s interview, Mr Blair also recalled his first meeting with Mr Adams and Mr McGuinness at Downing Street.

He added: “They came into the room in Downing Street and they were saying, ‘well this is where Michael Collins had sat with Lloyd George’ ... then Mo Mowlam, who was there at the time, sort of broke up this rather reflective conversation by saying, ‘yes, and that's the window that you fired the rockets in at John Major's government.’”

Meanwhile unionist leaders combined to condemn Mr Blair for “telling lies” to prevent the collapse of the peace process.

Mr Blair admitted to “stretching the truth ... beyond breaking point” in a series of phone calls over the 2006 New Year holiday to both Mr Adams and Ian Paisley.

He said Mr Adams had agreed to a special ard fheis if Mr Paisley made clear an endorsement of policing would lead to the restoration of the Executive and Assembly.

“I took horrendous chances in what I was telling each the other had agreed to — stretching the truth, I fear, on occasions past breaking point,” Mr Blair wrote.

He argued it was Ian Paisley’s “long and debilitating illness” which helped change him into a peace-maker, and relates how people “could never understand” when he would say how much he liked the former DUP leader and First Minister.

Ulster Unionist leader Sir Reg Empey said Northern Ireland was living with the “very real mistakes” made by Mr Blair’s approach.

“It has always been clear to some of us that the deal emerging from St Andrews was one done in haste and for the wrong reasons,” he said.

“Blair goes as far as to outline his interpretation being that Paisley wanted to leave behind something more profound and enduring (but) clearing Ian Paisley’s conscience is no basis on which to construct a deal on Northern Ireland’s future.

“That is what has allowed the insidious sabotage of the Northern Ireland Constitution that emerged with the election of First Minister changes.

“We are living with the very real mistakes that were made |in the then Prime Minister’s |approach.”

Senior DUP MP Gregory Campbell said that when negotiating with Mr Blair, his party’s emphasis always lay on actions not words.

“We never accepted words because we knew how easily they had been ditched in the past,” he said.