Revealed: Warning signs that could have stopped the Omagh bombing

Emails from FBI agent said to show that services had detailed picture of Real IRA before attack

The British and Irish governments will face demands this week for a new inquiry into their police and intelligence agencies after unpublished emails from an FBI spy raised fresh questions about what the authorities could have done to prevent the 1998 Omagh bombing.

A report, commissioned by families of some of the 29 people killed in the attack, claims that the bombing could have been prevented if three crucial strands of evidence had been linked, leading to increased security that could have disrupted the bombers’ plans.

The families are expected to renew their calls for a cross-border public inquiry, a year after their report was delivered to the two governments as part of their long-running campaign to learn the full story behind the Real IRA attack.

The report is thought to draw on hundreds of pages of emails between David Rupert – an American trucker-turned-informant who infiltrated republican paramilitaries – and his MI5 handler.

It is understood the emails provide detail on potential planning, locations and personnel for an attack in the run-up to the blast on 15 August, 1998, when a stolen Vauxhall car was packed with 500lb of explosives and detonated in the town centre.

The families say those details were not shared with police on either side of the border before the attack or during the investigation to find out who was responsible.

The report is understood to say:

* a senior Irish police officer failed to pass to his counterparts in the North information that dissident republicans were trying to obtain a vehicle for a bombing, a claim previously rejected by the Irish government and police in the North;

* there is evidence to back claims – denied by the authorities – that the bombers’ car may have been tracked in the run-up to the attack with the help of the FBI;

* three pieces of evidence, from an anonymous tip-off and two informants, could have prevented the bombing if they had been brought together in time;

* the Rupert emails provided MI5 with material that was not passed swiftly to police investigating who was responsible.

Copies of the emails were obtained by the families, and sections were used in a civil case which saw them win £1.6m in 2009 against four men found liable for the murders.

The four included Michael McKevitt, the leader of the Real IRA, who was jailed in 2003 for 20 years for directing terrorism, in a case unrelated to the Omagh bombing. Nobody has been convicted for the Omagh attack. The families say the evidence in their report goes beyond what was revealed in two Panorama programmes, which included claims that on the day of the attack GCHQ was monitoring a phone number being used by the bombers.

Following those claims, a report by Sir Peter Gibson concluded that the attack could not have been prevented. It was one of a number of inquiries which examined issues including the sharing of evidence, the role of police in the south, and a review of what intelligence was picked up by GCHQ. The families say their inquiry, conducted by private investigators, raises questions that can be answered only by a full, cross-border inquiry.

Michael Gallagher, whose son Aidan was killed in the bombing, said: “When we started to read the emails, we started to learn the extent of the information that the intelligence services had.

“It was obvious from the emails that early in 1998 they had a handle on these people. They had identified the key players, they had telephone numbers. And they had sources quite close, if not at the top of, this organisation. So when it came to the point of the Omagh bomb, the knowledge they had was very extensive.”

The families believe the Rupert emails, along with warnings of a dissident operation from an agent for British military intelligence and an anonymous tip-off 11 days before the attack naming three men, should have prompted a security operation in Omagh that could have prevented the attack.

The families’ report is believed to have brought together an examination of a series of reports, witness statements and interviews with key figures involved in the investigation.They are due to give details of their findings at a press conference in Omagh on Thursday, a week before the 15th anniversary of the attack in the market town.

“We are still considering the options and we hope to reach a decision shortly” on the families’ demand for a public inquiry, said a spokesman for the Northern Ireland Secretary Theresa Villiers.

Timeline: The search for truth

15 August 1998: Blast rips through Omagh, killing 29 people after a series of contradictory warnings.

October 2000: Panorama broadcasts names of four men connected with the bombing.

December 2001: Report by ombudsman criticises police inquiry and says key intelligence was not passed to inquiry team.

August 2003: Michael McKevitt convicted of directing terrorism and jailed in charges unrelated to the Omagh attack.

September 2008: Panorama reports agencies monitored phones of suspected bombers.

January 2009: Sir Peter Gibson says the attack could not have been prevented .

June 2009: Families win civil claim against four men found liable for the Omagh bomb, who are ordered to pay £1.6m.

June 2012: Campaigners present questions they want answered.

August 2013: Families call for new public inquiry.