Chief Constable Sir Ronnie Flanagan tonight threatened legal action to clear his name after being accused of flawed judgment which could have damaged the chances of arresting the Omagh bomb suspects.
He warned he may go to the High Court when he hit back at Police Ombudsman Nuala O'Loan's devastating report into the investigation of the outrage.
She claimed the inquiry was undermined by defective leadership and poor judgment.
A furious Sir Ronnie declared: "I am astounded by these wild and sweeping conclusions".
Mrs O'Loan's damning report and the Chief Constable's stinging rebuke signalled the outbreak of an unprecedented row which stunned relatives of the 29 people killed in the August 1998 Real IRA bombing.
It also shocked the Government and the new policing structures which are at the heart of the peace process in Northern Ireland.
The families tonight called for an independent investigation - one of the key recommendations in the ombudsman's report.
Sir Ronnie, who is due to retire early next year, indicated he may bring in officers from Merseyside to implement key recommendations following an internal review.
A defiant Mrs O'Loan insisted: "I stand by everything."
Northern Ireland Secretary of State Dr John Reid called on all sides to study the report carefully and not to rush into judgment and play politics with the findings.
RUC Special Branch were accused of failing to pass on information to officers on the ground warning of a threatened terrorist strike to take place in Omagh on the day of the car bomb.
The first of two warnings was made 11 days before the attack, and a second claiming that a bomb was being transported across the Irish border into Northern Ireland was received three days in advance of the bombing.
Mrs O'Loan said the judgment and leadership of the Chief Constable and the Assistant Chief Constable Crime Raymond White had been seriously flawed.
She added: "As a result of that, the chances of detaining and convicting the Omagh bombers has been significantly reduced.
"The victims, their families, the people of Omagh and officers of the RUC were let down by defective leadership, poor judgment and a lack of urgency."
The police ombudsman called for a new investigative team from outside Northern Ireland to be called in and a review of the role of Special Branch to be carried out.
Mrs O'Loan refused to delay the release of the report until December 19 after the Chief Constable asked for more time to respond to the allegations.
He was in incandescent mood tonight when he hit back, escalating a row which threatened to overshadow the bewilderment and confusion on the streets of Omagh where families are still trying to come to terms with the failure to bring the dissident republican Real IRA bombers to justice.
Sir Ronnie claimed the ombudsman and her team had failed to take into account senior RUC officers' versions of what happened before and after the Omagh attack.
At Police Service headquarters in Belfast tonight, he alleged the ombudsman had reached "erroneous conclusions" in advance and had tried to support their predetermined assessment.
He also revealed neither he nor his senior officers had been interviewed about the charges levelled against them, including the central claim that they were guilty of defective leadership and poor judgment.
"If that was a conclusion reached as a result of a rigorous, fair investigation, I would not only resign, I would go on to publicly commit suicide.
"I think those are conclusions reached without ever having been put to me. It's a denial of natural justice without me ever having the opportunity to ask why and how do you come to those conclusions and without ever being given the opportunity to respond?"
PA