Families of Omagh bomb victims have vowed to take the Government to court after branding its decision to rule out a public inquiry into the attack as a feeble bid to hide from the truth.

Relatives made the defiant pledge to take judicial review proceedings after Northern Ireland Secretary Theresa Villiers said she did not believe there were sufficient grounds to justify a state commissioned independent probe into the 1998 Real IRA bombing.

The dissident republican attack, which killed 29 people, including a woman pregnant with twins, and injured more than 200, was one of the worst atrocities of the Northern Ireland troubles and inflicted the greatest loss of life in a single terrorist incident.

The event is dogged by controversy, with long standing allegations that intelligence and investigative failures by authorities on both sides of the border allowed the bombers to carry out the crime and get away with it.

Stanley McCombe, whose wife Ann was killed, said the anger he felt at the Government's decision would drive him onward as the families proceeded with legal action. He said: "If they want to try and hide the truth about Omagh, they can. But we'll flush them out at the end of the day. There are no hiding places. It's a democratic country and people have to know the truth." Michael Gallagher, whose 21-year-old son Aiden died in the August 1998 blast, added: "We'll do our talking in court."

Omagh was bombed just months after politicians in Northern Ireland signed the historic Good Friday peace accord that led to power sharing at Stormont. While no one has been criminally convicted, four republicans were found liable for the atrocity in a landmark civil case taken by some of the relatives and ordered to pay £1.6 million compensation.

Last month families who belong to the Omagh Support and Self Help Group outlined details of an independent report they commissioned into alleged intelligence failings in the lead up to the atrocity and with the subsequent criminal investigations. They had handed it to the authorities in London and Dublin a year previously and complained at the length of time the governments had taken to respond.

Ms Villiers said a current investigation into elements of the incident by the Northern Ireland Police Ombudsman was the best way to proceed. "I do not believe that there are sufficient grounds to justify a further review or inquiry above and beyond those that have already taken place or are ongoing," she said.

Kevin Skelton, whose wife Philomena was among the victims, is one of the Omagh relatives opposed to a public inquiry as his children want their mother allowed to rest in peace. He told the BBC: "I am making my position quite clear and I would have other families behind me in that, who are not interested in a public inquiry because they don't think it's going to achieve anything."

"We know the answers. I know there were dirty deeds done round Omagh and the Government, whether there is a public inquiry or not, they are going to bury them, and they have the power to do that," he said.