The Omagh bombing - later admitted by the dissident republican Real IRA - killed 29 people, including a woman pregnant with twins, and injured hundreds more.

Sir Ronnie: Due in Omagh on Thursday

Last December, the judgement and leadership of Sir Ronnie during the bomb investigation was described as "seriously flawed" in a report by Police Ombudsman Nuala O'Loan.

It also said that the RUC had information from informants about a planned attack in Omagh 11 days before the bombing, which had it been passed on and security checkpoints put in place, may have deterred the bombers.

Sir Ronnie Flanagan has prepared two documents rebutting the report which have been exclusively obtained by BBC Northern Ireland's Spotlight programme.

The chief constable said the police service had "nothing to hide about its conduct of the Omagh investigation and is more than ready to take any steps to reassure the public".

Colm Murphy: Convicted of conspiring to cause the Omagh bombing

In an 87-page document, Sir Ronnie covers what he calls "significant factual inaccuracies, misunderstandings, material omissions and unwarranted assumptions".

The second paper deals with Nuala O'Loan's six recommendations on the way forward.

The ombudsman said an outside investigator should be put in charge of investigation.

Instead, the chief constable's response has been to appoint a senior detective from Merseyside to advise Detective Superintendent Brian McArthur who is heading the Omagh investigation.

In his response document, Sir Ronnie says the Merseyside adviser will have unrestricted access to all material requested, and will "quality assure" the investigation.

The adviser is also to oversee the implementation of the recommendations of the police's own internal review of the bombing investigation.

The internal review made more than 270 recommendations.

It is understood the Policing Board already has Sir Ronnie's response.

Gerry Toner who lost his daughter in the bombing, said the meeting with Sir Ronnie would be "very serious."

Meanwhile, the man behind the ombudsman's report said it was not too late to catch the bombers.

'Unreliable informant'

Martin Bridger, who is the Ombudsman's deputy director of investigations, said despite mistakes made by the police he believed the investigation could still bring the bombers to court.

Martin Bridger: "Opportunities were missed"

"I think there were early opportunities that were missed," he told the Spotlight programme.

"But from everything I've seen over the last few months, I think there is still a very real prospect there that these people could be brought to justice."

However, Martin Bridger also revealed the ombudsman's office received information which cast doubt on the reliability of an informant Kevin Fulton who allegedly gave warnings about a planned bombing to special branch.

The ombudsman's report did not include this and suggested that Fulton was deemed by the police to have been a reliable source whose tip-offs should have been trusted.