The Men Behaving Badly actor was filming an interview for Piers Morgan’s Life Stories when he made the revelation.
He admitted: ‘I feel sorry for how the situation was dealt with and I feel sorry for how emotional Les seemed to become. It was very difficult for him and for that I’m very sorry.’
Neil and actress Amanda met when they filmed Happy Birthday Shakespeare for the BBC in 2001.
Their affair sadly led to the eventual breakdown of Amanda’s marriage to Les.
When Piers asked Neil if he had since apologised to Les over the affair, the actor replied: ‘No, I didn’t. I’m not positive over what there is apologise about. I don’t know what the whole situation was, to be perfectly fair to everybody.’
He continued to give his reasons for not personally apologising closer to the time.
He said: ‘I think enough was said about it. This was a very short fling. I didn’t have representation at the time, in terms of PR and this was the first time I’d really come under the cosh.’
Britain’s Got Talent judge Amanda had previously spoken out about her relationship with the actor, saying: ‘The backlash over my affair with Neil Morrissey was the worst thing that ever happened to me.’
Neil is now dating an American lawyer, who he describes as ‘a strong woman who is not interested in celebrity.’