Politicians have condemned what has been termed a "hit list" allegedly issued by the IRA, containing the names of 25 people in the Downpatrick area.
Outcry, a human rights group based in Downpatrick, claims it has seen a list drawn up by senior republicans determined to "clean up the town".
The 25 people the list is reported to name are aged between 16 and 25, and are to be beaten or expelled for alleged antisocial behaviour.
The Ulster Unionist Party deputy leader, Mr John Taylor, said he was "revolted" by the existence of such a list and called on the IRA to "publicly withdraw these cowardly threats immediately before any more deaths and injuries occur".
"I am revolted to learn that the Provisional IRA has targeted young Catholics in the Downpatrick area for their brand of summary justice. Kangaroo courts are no substitute for the proper legal process and are completely unacceptable to me and to all right-thinking members of the community, Catholic and Protestant," Mr Taylor said.
"I cannot but conclude that the IRA in Co Down has taken Dr Mowlam's decision last week as a green light for more beatings, killings and torture. The blame rests at her door," he added.
"I hope and trust the community will unite to repel the dark forces in our society. I urge the local clergy, particularly the local Catholic hierarchy, to take a stand for the human rights of local teenagers."
Meanwhile, a Sinn Fein Assembly member, Mr Alex Maskey, said the fact that republican paramilitaries were taking the law into their own hands was due to a "policing vacuum" in the North.
"We have an absence of a credible policing service and that is the core of the problem. What we need is a police force that members of both communities can rightly go to and should go to," he told BBC Radio Ulster.
Mr Maskey said he did not take seriously unionist condemnation of expulsions of young Catholics. "We have never heard them concerned about our community in the past and I think we should take with a huge dose of salt their alleged concern at the moment," he added.
The director of the Northern Ireland Human Rights Bureau, Mr Vincent McKenna, claimed last night that a 17-year-old youth had been ordered to leave the country by loyalist paramilitaries.
Mr McKenna said the Ulster Defence Association issued the threat against the teenager from the Shankill Road in west Belfast at 10 p.m. on Monday. They accused him of being a police informer and ordered him to leave the country within 24 hours.