Reaction to IRA statement: Robert McCartney's aunt said the IRA statement and its offer to shoot those responsible for his murder was "highly insensitive".
Margaret Quinn said: "Killing somebody is irreversible. At the moment these people are suspected. To kill suspects, how would anyone ever know if those suspects were the people who were involved?"
British prime minister Tony Blair's official spokesman last night echoed the demand of Mr McCartney's family that his killers be brought to justice, and noted this was also the view expressed by Sinn Féin president Gerry Adams at last weekend's ardfheis.
Reacting to the IRA statement, the spokesman said: "Clearly threats of any kind are unacceptable. The family have made clear throughout that they want those responsible held to account through the courts. That is our position, and it also happens to be the view expressed by Gerry Adams on Saturday."
Northern Ireland secretary Paul Murphy told BBC Radio 4 Mr McCartney's family were right: "There should be due process, there is no place for summary justice. The idea that we can solve the problem of one murder by committing another is absolute nonsense."
Sinn Féin distanced itself from the offer to have the murderers shot. Its justice spokesman Gerry Kelly claimed the party was amazed at the concentration on this issue, which was but one sentence from a lengthy statement.
He said: "This is a very important statement. The IRA is saying it wants people to come forward. It has ordered people within its organisation to go forward and give witness statements, and it has also asked people not in its organisation to come forward."
Mr Kelly said the statement enhanced the call by the McCartney sisters to have justice secured in court. He added he believed there was no threat to anyone who wanted to co-operate with the investigation and any judicial process.
Asked by The Irish Times how he viewed the IRA offer to shoot Mr McCartney's killers, Mr Kelly said: "It did not happen and I am glad it did not happen . . . The IRA has ordered people to come forward and encouraged anyone else who has information to come forward. I think that is very positive."
Asked if it was his understanding that the IRA was instructing its members to go before courts which other IRA members have refused to recognise, Mr Kelly said: "Yes, that's clear. That is very clear."
The Rev Ian Paisley called for Sinn Féin leaders to be arrested. The DUP leader said: "This is the type of justice so-called that the IRA is used to dispensing. It is their declared intent to murder."
He added: "When considering the offer to murder, people need to remember those who, according to Michael McDowell, are the leaders of the IRA. It is time for the government to arrest Sinn Féin-IRA leaders."
A senior Ulster Unionist said the statement was perhaps the worst he had heard from the IRA. Sir Reg Empey said: "This is an appalling statement from a movement that has clearly learnt nothing over 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. It is a sick and desperate statement that will be completely beyond sense to all rational human beings."
The SDLP South Down MP Eddie McGrady said: "This obscene proposal by the IRA to kill the alleged murderers of Robert McCartney is sinking to the lowest depths of terror in the community."