Northern Ireland’s Assembly is to be asked to consider support for the establishment of cross-border legal powers to obtain security force intelligence evidence into the Omagh bomb, the Belfast Telegraph can reveal today.

A motion will be placed before the Assembly next week by the Alliance party calling for the creation of a “formal, cross-border, legally binding process” which is designed to secure “full disclosure from the intelligence services and security forces in the United Kingdom and the Republic of Ireland,” in a bid to establish what relevant information they had before and immediately after the 1998 attack.

Twenty-nine people and unborn twins were killed in the attack, which was the worst single atrocity of the Troubles.

Alliance leader David Ford said that the people of Omagh have a right to know the full facts “about the tragic events of Saturday 15 August 1998”.

“This bombing resulted in the biggest loss of life throughout the whole of the Troubles and any right-thinking person should support this call for total disclosure of all information about the incident,” he said.

“Clarity and a full account of events are the least that those affected by the bomb deserve. People’s lives were ripped apart by this bombing and victims continue to suffer because of all the unanswered questions. Given the cross-border aspects of the crime, many will not gain closure without a full cross-border investigation process.”

Michael Gallagher, chairman of the Omagh support and self-help group, said: “The inquiry into Omagh is not just important to the Omagh families, but to everyone in this island and beyond.

“We should learn what was done well and what was not done well, and those lessons should be passed on to others so that we are better prepared for any future terrorist attack or disaster. The inquiry should never take away from those who were responsible for planning and preparing this evil act.”

No one has ever been prosecuted for the Omagh atrocity and it has been a long battle for justice for the families.

Last December, south Armagh electrician Sean Hoey (38) was cleared of involvement following a lengthy trial.

A civil case brought by the bereaved families against five men they believe were involved in the 1998 bombing is currently being held.

The Omagh families have always raised questions over the investigation into the bomb and the controversy over the investigation reignited last month after it emerged that the UK’s eavesdropping centre GCHQ had been monitoring the Real IRA bombers on the day of the massacre.