Euro-MPs launched bitter attacks on Sinn Fein and the IRA tonight over the murder of Robert McCartney.
They said his family deserved justice and demanded that the European Union fund a civil action to bring his killers to justice.
It was also claimed that the current criminal police inquiry is thwarted by lack of co-operation.
The cross-party condemnation came in a debate in Strasbourg triggered by Mr McCartney's sisters' plea for help in breaking down walls of silence.
Three McCartney sisters - Gemma, Paula and Catherine - were in the public gallery of the Strasbourg chamber to hear overwhelming support for their campaign - and strident demands for Sinn Fein and the IRA to co-operate.
Fine Gael MEP Avril Doyle, one of the key proposers of a joint motion urging the use of EU funds to back a civil legal action in Northern Ireland if necessary, said the McCartney family had conducted a "courageous, dignified and determined pursuit of justice".
She went on: "Robert McCartney's vicious beating and stabbing to death was ordered by a commander in the Belfast brigade of the provisional IRA following a minor dispute between the commander's uncle and the group with which Mr McCartney was socialising.
"Robert McCartney was in the wrong place at the wrong time but this was no minor barroom brawl as some have disgracefully attempted to portray it. His brutal beating and stabbing was a serious and savage attack, which bore all the hallmarks of a politically motivated IRA murder."
Ms Doyle claimed the killing was "perpetrated by up to 12 killers, a significant number of whom are known members of the provisional IRA."
Democratic Unionist Party MEP Jim Allister saluted the "remarkable bravery" of the McCartney sisters in the wake of a "foul murder" carried out on the order by hand signal from an IRA commander that a knife should be used to kill.
An IRA unit then disposed of the knife and conducted a clean-up. Then, he said the intimidation brigade stepped in. The "cut-throat psychopath" behind the killing remained "publicly proclaimed", and the one who ordered the killing still "struts the streets of Belfast", he said.
He named three men he called on to tell what they knew of the "horrific events in the alleyway".
"Sinn Fein-IRA could secure justice, but their priority is to protect their own."
Ulster Unionist Euro-MP James Nicholson said the level of European support for the McCartney sisters and Mr McCartney's fiancee, Bridgeen Karen Hagans, reflected abhorrence of terrorism and frustration with Sinn Fein: "These brave women have shown that they won't be intimidated, despite the brutal manner of Robert McCartney's murder and the conspiracy of silence that surrounds it.
"Sinn Fein and the IRA have been seriously embarrassed by the public outcry this killing has caused. The European Parliament is showing its solidarity for the McCartney sisters, its contempt for the murderers and thugs in the IRA, and its anger at Sinn Fein's refusal to act decisively against those responsible."
The motion on the table, backed by more than 600 MEPs - although not the two Sinn Fein members - condemned "violence and criminality by the self-styled 'Irish Republican Army' (IRA) in Northern Ireland, in particular the murder of Robert McCartney".