Ireland, who could make his Newcastle debut against Everton at the weekend if he can shake off a thigh injury, was signed for Villa by Martin O'Neill but a day later the manager quit the club.
Ireland featured very rarely under new boss Houllier, making just eight starts in all competitions, and speaking in an interview with French football magazine So Foot, he hit back at the Frenchman.
"After 15 matches on the bench Houllier told me to stay at home," Ireland said. "I trained during the week and on Fridays he told me, 'no point you coming, you are not in the team'.
"Yet I was the best player in training. It was my team that won in every session. One of the few times he played me, we drew 0-0 at Chelsea and I ended up man of the match.
"Apparently that didn't matter to him. I was stuck with being paid for doing nothing at all. I was left to myself. I had to pay out of my own pocket for medical treatment. Can you believe that?"
Ireland was also unhappy at being asked to move to Birmingham, which he branded "a c**p city".
"Houllier asked me to come and live in Birmingham because it was taking me 75 minutes to come to training. But there were 15 players in the same position as me. Some came from London and took more than two hours, but he only asked me to move," Ireland added.
"For a start, Birmingham is a c**p city and I wasn't going to make the effort, especially as I wasn't playing. Might as well be in Manchester if I had to stay home on match days."