Relatives of the Omagh bomb victims will tomorrow hold talks with Northern Ireland Secretary of State Owen Paterson on a new report they commissioned into the atrocity.
They believe they have uncovered fresh evidence on the security force response to the Real IRA bomb plot which killed 29 people in the Co Tyrone town more than a decade ago.
Representatives of some of those who lost loved ones in the bombing will meet Mr Paterson in Belfast to discuss the findings.
Campaigners have previously demanded a cross-border inquiry into whether the authorities in the North and in the Republic of Ireland could have done more to prevent the bombing.
A spokesman for the families said of the meeting: “We see this as an important step towards a public inquiry and are looking forward to updating the Secretary of State.”
The 1998 car bomb planted by dissident republicans opposed to the peace process caused the largest loss of life of any single attack of the Troubles.
The victims included a woman who was pregnant with twins.
Earlier this year Michael Gallagher, whose 21-year-old son Aiden was murdered in the attack, said the report had uncovered new information.
He declined to comment on the nature of the new evidence, but predicted it would add pressure on the British and Irish governments to order an inquiry.
The Omagh Support and Self Help Group commissioned the report from a group of London-based consultants who have interviewed key figures associated with the case.
The consultants have also examined material already compiled on the bombing.
The documentation includes police reports from both sides of the border, a probe carried out by the Police Ombudsman in the North, and a British Government-sponsored review of how intelligence on the attack was handled.
The relatives also secured disclosure of other documents linked to the case.
Four men have been held responsible by a civil court for the bombing. A man accused of murder was cleared by a court in 2007.
A 2001 report by former NI police ombudsman Nuala O’Loan criticised poor judgment in the Royal Ulster Constabulary in the years after the attack.