PSNI Chief Constable Hugh Orde has said he believes the Provisional IRA was behind the multi-million pound Belfast bank heist last month.
Speaking at a press conference in Belfast Mr Orde said it now made "operational sense" to attribute blame "and it will allow us to get on with the inquiry".
Hugh Orde
"What I can say is, on the basis of the investigative work we have done to date, the evidence we have collected, the information we have collected, the exhibits we have collected, and bringing it all together and working through it, in my opinion the Provision IRA were responsible for this crime", Mr Orde said.
Northern Bank revised upwards from £22 million to £26.5 million, the amount taken in the raid.
Mr Orde refused to go into detail about how he reached the opinion. "We are not compromising this inquiry," he added.
He said there would be consequences to his statement but they were "for other people to deal with. They are not for me to comment on, I have no intention to comment on them."
Unionist politicians previously warned of "dire" political consequences if the IRA is officially blamed. It almost certainly puts back until after the British general election, expected in May, any renewed drive to restore devolution by the British and Irish governments.
The Taoiseach, Mr Ahern, said Mr Orde's claim was a "serious setback" for the peace process and had damaged "levels of trust and confidence."
Democratic Unionist deputy leader, Mr Peter Robinson said the announcement had raised the bar for Republicans in the peace process. "It is up to the Prime Minister to say how he will move the process forward. This has actually strengthened the argument for a decontamination period and it effectively the bar is higher for Republicans," he said.
However, Sinn Féin's chief negotiator, Mr Martin McGuinness, said Mr Orde did not produce "a scrap of evidence" and was an attempt to marginalise his party.
No one has been arrested or charged in connection with the robbery. The chief focus of the police searches, however, was in nationalist west Belfast, triggering speculation that the IRA was behind the December 20th raid.
Mr Orde also said Northern Bank intended to withdraw all their bank notes and re-issue them in a different style and colour. He said the bank's move made the robbery the "largest theft of waste paper in the living history of Northern Ireland".
He added: "This was not a victimless crime... It was a very violent and very brutal crime".
This morning Mr Orde met the Policing Board chairman, Sir Desmond Rea, and deputy chairman, Mr Denis Bradley.
Earlier, Mr McGuinness, said the IRA was not involved. The organisation yesterday said that attempts to criminalise its members would fail but stopped short of denying the Belfast heist outright.
Speaking on the Today programme on BBC this morning, Mr McGuinness confirmed he had spoken to the IRA after the robbery and was told that it was not involved.
Speaking in Belfast this morning Mr McGuinness reiterated his view that "there are clearly elements within the British system and unionism intent on wrecking the peace process and of using the robbery in Belfast as a pretext for this. They must not be allowed to succeed."
Sinn Féin president, Mr Gerry Adams, yesterday insisted that the IRA was not involved and the organisation itself said attempts to criminalise it would fail.
His comments came after the IRA issued a New Year statement yesterday carrying the official P. O'Neill signature. The statement complained that a comprehensive deal that would have seen the IRA decommissioning and entering a "new mode" was prevented by "an unachievable demand for humiliation".
The statement did not refer specifically to the robbery, although it did say it rejected "attempts to criminalise our volunteers".
