Calls for an inquiry into "forgotten babies" from institutional homes in Northern Ireland who were buried in mass graves have still not been answered 18 months later, campaigners claimed.
At least 11,000 people are interred in west Belfast on land which used to form a nature reserve.
Hundreds of infants from homes for unmarried mothers and their offspring were routinely placed there without ceremony or marker during the last century, Amnesty International said.
Patrick Corrigan, director at Amnesty in Northern Ireland, said their short lives could be due to neglect or abuse while in care.
"We have asked the First and Deputy First Minister (at the Stormont Executive) to establish an inquiry into Mother and Baby homes here, as has been promised in the Republic.
"Unfortunately, 18 months on from the original request to ministers, families are still awaiting a response."
Earlier this year a mass grave for babies was found at a home in Tuam, Galway, in the west of Ireland and Mr Corrigan said it was more important than ever to discover of the truth of what happened at Mother and Baby Homes in Northern Ireland.
A retired judge, Sir Anthony Hart, is chairing the Historical Institutional Abuse (HIA) inquiry into institutional abuse at religious-run children's homes in Northern Ireland dating back to the years after the First World War, but not including this particular group.
According to Office of the First Minister and Deputy First Minister (OFMDFM) minutes an official "discussed a possible new dimension to the HIA regarding mother and baby homes throughout the island of Ireland" earlier this year.
Mother and Baby homes were mainly established by religious bodies. Premarital pregnancy was stigmatised and women were sometimes taken to these homes by parents or social workers.
A Christmas flower-laying ceremony at Milltown Cemetery in west Belfast where the mass graves are located was organised by relatives of those buried and Amnesty International, which is calling for an inquiry into the homes. This is the first year civic leaders including Belfast's Lord Mayor Nichola Mallon have taken part.
Among those present were Fionnuala McGoldrick, who was born in Marianville Mother and Baby Home in south Belfast, as was her older brother Paul, after her young unwed mother was sent there. He died in another home from pneumonia seven months after he was born in August 1972.
Ms McGoldrick began the search to find her brother four years ago and earlier this year obtained records that confirmed he was buried at the Bog Meadows on the edge of Milltown Cemetery.
Toni Maguire, archaeologist and chairperson of Milltown Action Committee, whose uncle is buried there, said: "Today we pay homage to all those who are buried here.
"We must mark the graves which currently lie in this ground in such an anonymous way, to show that we remember them, but also to demonstrate that society recognises their existence."
Ms Mallon laid flowers at the unmarked plots to remember the babies and other poor and marginalised citizens buried there.
They include so-called "limbo babies" - unbaptised children denied a burial on consecrated ground.
This was because of a piece of Catholic theology according to which stillborns or those who died shortly after birth who had not been baptised could be denied a cemetery burial. Their souls could not go to heaven but would remain in limbo.
In west Belfast families discovered that their loved ones, some of them "limbo babies"', were buried in a wildlife reserve on the edge of the cemetery. Their mass unmarked graves had been sold through error by the cemetery.
Following protests, in 2009 the plot of land was handed back to Milltown Cemetery. The church authorised a survey using ground-penetrating radar to determine just how far into the bog meadows the graves might extend.
At least 400 infants from mother and baby homes are interred there but that number may be much higher, campaigners said.
A spokesperson for the OFMDFM said: "The primary purpose of the Historical Institutional Abuse (HIA) inquiry is to investigate whether there were systemic failings by institutions (apart from schools), or the state in their duties towards those children in their care under the age of 18.
"Mother and Baby homes were not established principally for the care of children and would have had many residents over the age of 18.
"To the extent that the inquiry has received applications from people who spent time in a home of this type, while under the age of 18, these will be considered.
"Until all applicants have been interviewed it will not be possible for the inquiry to make a final decision on whether these cases properly fall within the terms of reference or indeed whether there is any indication of systemic abuse."