The Ulster Unionist Party has described as "sick and desperate" an IRA statement which admits the organisation offered to shoot the alleged killers of Mr Robert McCartney.
Speaking following the latest IRA statement this evening, senior Ulster Unionist Sir Reg Empey said it was an "appalling statement" from a movement that had clearly learnt nothing in recent weeks.
"The fact that this group is offering murder as a form of justice should be the wake up-call that the governments urgently need. These are the people that they would have democrats share power with," he said.
"This latest statement proves unequivocally how far we are away the completion that we have been calling for. Only the intervention of the McCartneys has prevented further murders. It is a sick and desperate statement that will be completely beyond sense to all rational human beings."
The SDLP's South Down MP Eddie McGrady said the "obscene proposal" by the IRA to kill the alleged murderers was "sinking to the lowest depths of terror in the community".
"Irrespective of what crime a person is accused of, we must always safeguard the fundamental right of a fair trial, and if found guilty, a fair sentence. This appalling proposal is an extremely dangerous slide into anarchy and is a threat to the entire community of Northern Ireland," Mr McGrady said.
"It is a gross affront to all standards of decency, justice and the law. And would also fly in the face of the demands of the victims' family who have quite correctly demanded that the due processes of the law be brought to bear on the killers of their brother."
"Gerry Adams told us at the Sinn Fein Ard Fheis that he opposed shootings. What does he think of this? Does he think that the IRA have the right to maim and murder? Sinn Fein must state clearly if this is the kind of policing and justice that they wish to bring to the community in Northern Ireland."