Members of the Mother and Baby Homes Commission have refused to appear before an Oireachtas committee for a third time.
They had been asked to explain comments from one of the members about how much witness testimony was included in the final report.
In a letter to the Oireachtas committee, the commission said it is not true to claim survivor testimony was discounted.
Committee chair, Sinn Féin's Kathleen Funchion, said it is disappointing the commission members will not take questions.
"Another smack in the face for everybody whose trying to get genuine answers to this whole situation.
"They have refused again, for the third time now, to come before the committee to answer any questions.
"We're really obviously annoyed, very frustrated - and I just think at this stage now, this report absolutely cannot stand and it really needs to be scrapped."
'A useless exercise'
Last week campaigner and historian Catherine Corless told Newstalk survivors giving testimony was 'a useless exercise'.
It came after a member of the group, Professor Mary Daly, spoke about the work of the commission on an academic webinar - prompting backlash from survivors.
Ms Corless said: "It has been a revelation really, to hear Mary Daly saying precisely what we felt and what we thought from the start: that it was a terrible report, we weren't satisfied, a number of the survivors were very upset and hurt over it.
"It was just left at that and we had hoped that the committee would come back to the Oireachtas and speak - maybe with a selected group of survivors - to tell us exactly what happened.
"And now we realise that they knew all along - the committee had never intended to use the survivors testimonies at all.
"They went up and they felt they were giving their testimonies so that justice would be served to them and to their families.
"But now we realise that it was a useless exercise in the first place, and why they did is beyond me.
"It showed no respect, absolutely, for survivors - it wasn't survivor-orientated at all".
She added that the approach of the Mother and Baby Homes Commission was "a lovely way of just covering up everything again."
While Minister Catherine Martin said the commission had shown a lack of respect and compassion to survivors.
She pleaded with the commission to come before the Oireachtas.
"I think it's really disappointing that a member of the commission chose to speak in this closed academic venue - when you consider that the Oireachtas committee has issued two invites, they're issuing a third invite today, and I really think that's where the focus should be now.
"Yes it's a lack respect to the Oireachtas committee - but it's the lack of compassion and the hurt and the disregard for that, that is causing more pain to those who are already suffering.
"And I really plead to them.
"I understand the Oireachtas committee will issue a third invitation, and I would plead with them to do the right thing.
"Show compassion and come into the Oireachtas committee, answer the necessary questions where the survivors can listen and give them that at the very least".
Additional reporting: Jack Quann