Lorraine Walsh of the 221+ group has resigned as one of the patient representatives on the CervicalCheck steering committee.
She made the announcement on RTÉ's Prime Time.
Ms Walsh, one of 221 women whose smear tests were read incorrectly, was invited onto the CervicalCheck steering group last year as a patient representative.
The announcement of her resignation comes after a review of CervicalCheck was published, which showed that in 159 cases there were missed opportunities to prevent or diagnose cancer earlier.
The UK's Royal College of Obstetricians and Gynaecologists, which carried out the review, says there were serious consequences for the women concerned.
However, it said the screening programme was performing effectively.
Ms Walsh said she wished she could tell the women of Ireland she had confidence in the report but that she did not.
She said: "I wish I could tell the women of Ireland I have confidence in that report. I don't want to be telling them I don't have confidence in this. But I absolutely don't.
"The revelations of the last number of months have forced me to examine my own conscience and when I got to a stage when I couldn't sleep at night, I had to resign and I had to leave the CervicalCheck steering committee as the patient representative on it with Stephen Teap."
Ms Walsh said a few months ago they learned that information coming through from the Royal College of Obstetricians and Gynaecologists to the HSE was inaccurate.
"Even as late as early October, of 581 reports, half of them had to be returned because the detail in them was inaccurate," she said.
She said she spoke to the committee and Minister for Health Simon Harris about her concerns surrounding inaccuracies in reports and she felt that she was not being listened to.
Describing her own situation and that of the other women affected by the CervicalCheck controversy, she said "lives have been robbed".
"It is so different when you look at having a cancer diagnosis and realise it could have been avoided. It is so hard to come to terms with that," she said.