The chairwoman of a Stormont investigation into clerical child abuse and mother and baby homes has resigned due to ill health, alleged victims said.
Norah Gibbons was the independent chairwoman of the Executive's inter-departmental working group.
Academics from Queen's University in Belfast and Ulster University have been asked to spend a year examining their operation between 1922 and 1999.
They are due to interview former residents and comb government and institutional records.
Patrick Corrigan, Northern Ireland programme director of Amnesty International, said: "Our thoughts are with Norah Gibbons and we wish her a speedy and full return to health.
"Women from mother and baby homes in Northern Ireland have told Amnesty International that they suffered arbitrary detention, ill treatment, and the forced adoption of their babies - criminal acts in both domestic and international law.
"Meanwhile, more and more clerical abuse victims are coming forward to reveal their suffering at the hands of abusive priests and gross failures by church and state authorities.
"Serious allegations of abuse must now be met with investigations with the necessary hallmarks of independence, effectiveness and transparency.
"Victims have long called for public inquiries into these serious abuse allegations. They deserve to be heard."
The resignation has led to the cancellation of planned meetings on Tuesday with victims, Amnesty International and others.
Eunan Duffy was born in the Marian Vale Mother and Baby Home in Newry before being taken from his mother against her will and placed for adoption and is calling for a public inquiry into alleged abuse which took place in the homes.
He said: "I cannot believe that, after a year of waiting to meet with government officials who are making key decisions about our lives, the chair has resigned and the meeting has been cancelled."
He added: "We are now calling for a fresh approach, one where the victims are listened to."
As recently as the 1980s, newborn babies were being forcibly taken from their mothers and given up for adoption by nuns in Northern Ireland's laundries, women forced into institutions in Belfast and Newry after becoming pregnant have claimed.
Because they were adults they did not fall into Sir Anthony Hart's public inquiry into child abuse in institutions.
Victims have demanded their own public inquiries.