Fionnula Flanagan (75) called Weinstein "repulsive" and a "creep" as she said she hopes the uproar surrounding the allegations helps other victims of sexual harassment worldwide to speak out.
Almost a dozen women have accused Weinstein of harassing them - including A-listers Angelina Jolie and Gwyneth Paltrow.
Weinstein - the producer behind Oscar-winning films such as The English Patient and Shakespeare In Love - denies any wrongdoing.
Dubliner Fionnula worked with Weinstein on award-winning Transamerica and The Others and she called the claims "an open secret".
Speaking on Liveline on RTE Radio One, she said: "He was at all the parties, a lot of which he gave.
"He never made any advances towards me but by the time I worked on The Others on Transamerica I was no longer a 20-year-old actress, it seems to be that it was actresses who were very young that he behaved appallingly to."
She continued to say that although he never made any advances towards her, she still felt he wasn't to be trusted.
Fionnula claimed: "I don't think he's as powerful as he used to be by any means, certainly not in the last few years.
"He was also notorious for breaking his word on business dealings so my impression was that he was not to be trusted by any means."
She said: "He was a powerful person who could make or break a career and that's what people feared, people were nervous about that.
"If you want to work, and you have a right to work, he was just one producer but he was a powerful producer.