A row has broken out between Northern Ireland's Chief Constable and a former police watchdog after she said the Omagh bomb could have been prevented.
Former ombudsman Nuala O'Loan investigated police actions in the lead-up to the bomb and, in a report published in 2001, said she did not know whether the bomb could have been prevented.
However, speaking on Wednesday morning, the 20th anniversary of the blast which killed 29 people, including a woman pregnant with unborn twins, Baroness O'Loan said she now believes it could have been stopped.
But Police Service of Northern Ireland chief George Hamilton has insisted officers could not have prevented the blast.
"The former police ombudsman, Baroness Nuala O'Loan, has today alleged it is her firm view that the bombing could have been prevented," he said.
"I consider this comment to be inaccurate, unfair and unreasonable.
"Police were not in a position to prevent the Omagh bombing."
He added: "I do not know what has led Baroness O'Loan to a conclusion that differs so much from her remarks of 2001.
"Considerations around a public inquiry into the Omagh bombing are a matter for Government."
Baroness O'Loan later responded to Mr Hamilton remarks, standing by her comments.
"It is my understanding of the further information which has emerged, some of which I am not in a position to talk about, but we have seen work by very prominent journalists and we have seen the various inquiries by (Sir Peter) Gibson and people like that," she said.
"And we can see Gibson very carefully choosing his language about the reasonableness of the police actions in disclosing or not disclosing intelligence.
"We know that 78% of the intelligence was not disclosed, we know that there is a body of evidence and intelligence now about the tracking of people, intercepted telephone calls, so there is a lot more.