Republicans have been accused of "lying through their teeth" after murdering victims they blamed for passing information to the British security services during the Northern Ireland conflict.
Jean McConville, a widowed mother-of-10, was among 17 people abducted, killed and secretly buried by republican paramilitaries during the Troubles.
Even though a former IRA boss claimed Gerry Adams ordered her murder, the Sinn Fein president again insisted in a special television documentary that he had nothing to do with the young mother's death.
Senior Democratic Unionist Edwin Poots said: "Someone is lying through their teeth."
An Assembly motion noting a television documentary on the Disappeared and calling on those with information to help the search for the bodies was passed without going to a vote tonight.
Mrs McConville was killed after she went to the aid of a fatally wounded British soldier outside her home in west Belfast's Divis flats. The IRA claimed she was an informer.
Her remains were finally found at Shelling Hill beach in County Louth in the Irish Republic in August 2003.
Ms McConville's IRA killers tried to silence her son days after she vanished, it has been revealed.
Michael McConville, who was 11 when his mother was snatched from her west Belfast home in 1972, was abducted, beaten and threatened at gunpoint by young republicans intent on keeping her abduction quiet.
Mr Poots, a member of the power-sharing ministerial Executive with Sinn Fein, claimed republicans had been offensive and obscene in their attitude towards the Disappeared.
"There is no desire in republicanism to tell the truth about these issues," he told the Northern Ireland Assembly.
"If they cannot tell the truth about these issues, about their murky past on these issues, then how can we expect them to tell the truth on any other issues?"
Sinn Fein Deputy First Minister Martin McGuinness has said the targeting of the Disappeared was cruel and unjustified.
His party colleague Raymond McCartney said: "This was wrong and it was unjust and we must do all that we can to bring this injustice to an end."
Ulster Unionist leader Mike Nesbitt said only half the bodies were found due to information submitted by republicans.
Nationalist SDLP MLA Dominic Bradley recited a poem which one of the victims' families gave him. He said those who demand justice, equality, human rights and the truth about the past must afford the same rights to others who yearn for them.
"The overwhelming majority of families have had the consolation of mourning and burying their dead," he added.
"Although those ceremonies may not have wiped away every tear, they provided the possibility of closure on the grief, sorrow and pain of the traumatic death of a loved one.
"The families of the Disappeared who have not yet had the remains of their loved ones returned to them have not had even that possibility opened to them. They have been left - in many cases for decades - wondering about the fate of their loved ones, arriving at their own conclusions and awaiting the recovery of their remains."
DUP MLA Paul Givan was incredulous that republicans had told assembly members to search their consciences.
"A republican movement that would not know a conscience, an organisation that is morally bankrupt and yet have the audacity to come in here and tell us to search our consciences."
Sinn Fein South Down MLA Caitriona Ruane read out a letter from a relative of one of the Disappeared which thanked republicans for passing on information.
"That was a wrong that can never be righted. I can assure this house that Sinn Fein will do everything we can to help the families whose (relatives') remains have have not been recovered," she said.
An amended motion was passed without going to a vote.