The Taoiseach has said he did not suspect there was corruption and wrongdoing going on at Cabinet level when he first became a minister in 1987.
In an interview on RTÉ radio's Gerry Ryan Show yesterday, Mr Ahern also said that, while he had learned a lot from the former Taoiseach, Mr Charles Haughey, he was very different from him in temperament. While there were "a few bad downsides" to Mr Haughey's record, he had also done many positive things.
Asked why he thought there had been such an extent of wrongdoing in the late 1980s, he said: "The difficulty was that there were no rules. People just assumed that the highest of standards of probity and controls were in place and it got shoddy and people did wrong things."
He said he didn't suspect such activities were going on at the time. "In the ordinary run of things you get on with your work and you get on with things and you don't suspect that anyone is doing anything particularly wrong and you don't dwell on it."
He said standards had dropped in other countries, too, and the level of corruption uncovered in Ireland was not particularly high in international terms.
"In fact, things that have been found here in some areas would not touch what happened elsewhere, but there are a lot of things we can't be proud of", he said.
Asked if he had ever suspected any of his colleagues of wrongdoing, he said: "Back in the 1980s the answer is No . . . I did not suspect there was anyone going around giving huge donations or involved in any kind of corruption. It's a pity any of these things happened.
"Now we have changed the culture of the system, and we have put in tough controls, tough legislation, now people are accountable, they are scrutinised to an extraordinary extent. Maybe sometimes that's a bit over-bureaucratic, but it has to be done."
He said that, while he had learned from Mr Haughey when he was Taoiseach, he had not been shaped by him. You don't shape people to be like you, he said.
Mr Haughey's remark that Mr Ahern was "the most cunning, the most devious of them all" related to one particular negotiation, he said, but people kept repeating it about him.
He said Mr Haughey's projects had included the development of Temple Bar, the International Financial Services Centre, the development of the arts and the funding of tourism.
"There are many, many good things he did. Sure, there are a few downsides, bad downsides" but his contribution to the State's cultural revival and the development of important buildings at a time when there was very little money was important.
He also insisted that he was not moulded in Mr Haughey's image. "I would be different in temperament. Charlie could be tough, hard and ruthless, I don't have those traits and don't want to have those traits. People accuse me of exactly the opposite to him."