Speaking yesterday, the former Ulster Unionist leader said it was essential the authorities supported the civil action to try to get justice for the victims' families.

Said Lord Trimble: "It is now incumbent on the two governments to row in behind the families - that is the minimum at least that should be done.

"I urge Her Majesty's government and the Irish government to get behind these relatives now because we need a renewed joint effort from London and Dublin to achieve a successful outcome for those who have been so devastated by the Omagh bombing."

Lord Trimble declined to be specific about the assistance both governments could give to the Omagh relatives bringing civil cases against five republicans - Michael McKevitt, Seamus Daly, Liam Campbell, Colm Murphy and Seamus McKenna.

There is little expectation among the Omagh victims' relatives that potentially key witnesses under the protection of gardai, MI5 and the FBI will be allowed to give evidence.

The FBI has already indicated that it will not permit Dave Rupert - an agent who infiltrated the Real IRA - to either attend the hearing or give evidence via videolink from the US.

Another witness who could give evidence to the hearing is car thief Paddy Dixon who is being looked after within a Garda witness protection programme.

Former Garda detective sergeant John White has alleged that Dixon was asked by the Real IRA to steal a car for use in a bombing just two days before the attack.

Dixon recently gave evidence via videolink to the Morris Tribunal investigating Garda corruption in Donegal. The PSNI has been refused permission to interview him about the Real IRA's preparations for the Omagh attack.