Relatives of those killed in the Omagh bomb are to launch a campaign this week to raise £1 million for the costs of a civil action against those suspected of carrying out the attack.
Mr Victor Barker, whose 10year-old son James was killed in the 1998 bombing, said a number of politicians would attend the launch at the House of Commons on Wednesday.
Twenty-nine people and unborn twins were killed in the explosion.
A number of former Northern Secretaries including Ms Mo Mowlam, Mr Roy Mason, Mr Douglas Hurd and Sir Patrick Mayhew have pledged their support and Mr Peter Mandelson has donated £10,000. "We have already got around £180,000 but our advice is that we would need as much as a million," Mr Barker said.
He said the families intended to name between five and seven people in their action. All four individuals mentioned in a BBC Panorama programme late last year would be sued, he said.
Mr Barker said the relatives' aim was to bring those responsible to account, even if they could not be criminally prosecuted.
"We want to have these people we believe to be responsible answer questions about what they did. We want some form of justice and it's our only option at the moment," he said.
Security sources say the Garda and RUC know the identities of those involved in the bombing but have not been able to produce evidence to prove guilt beyond a reasonable doubt - the criminal standard of proof.
Mr Barker said he believed the Irish and British governments were doing all in their power to help but the major impediment was that potential witnesses were unwilling to speak, in some cases because of intimidation.
Mr Barker said Acting Assistant Chief Constable Eric Anderson, the officer in charge of the RUC's inquiry into the bombing, had indicated to the families that he would be willing to identify those responsible in a civil court.
Speaking to the Sunday World newspaper, Mr Anderson said: "I know who made the bomb and who planted it. I know the names of the entire bombing team."
Mr Anderson, who retires from the RUC next Saturday, told the newspaper he would name the bombers if that was what the relatives wanted. "If I'm asked in a civil court to confirm the names put to me, I will," he said.