The Minister for Justice has said Sinn Féin's leadership - Gerry Adams, Martin McGuinness and Martin Ferris - must accept direct personal responsibility for the setback in the peace process caused by the return to Ireland of the so-called "Colombia Three".
He said the IRA army council, which the leadership of Sinn Féin had "until recently [ been] personally mixed together with", had arranged for the men to go to Colombia to train Farc guerrillas in the use of "deadly weapons of terror".
The same people had also arranged for the men's return to Ireland. The damage done to the peace process would take a long time to repair. Mr Adams, Mr McGuinness and Mr Ferris had clear responsibilities in this regard.
In his first comments on the case since news broke three weeks ago of the men's return to Ireland, Mr McDowell said the Irish people should consider "whether the arrival back of these men under these circumstances is not being undertaken with a view to damaging the process of reconciliation" in Ireland.
"It could only have been done, because it was so fraught with difficulty and risk, with the collusion of the top management of the provisional movement and I'm talking about the army council.
"Each and every member of the army council at the time bears personal responsibility for the difficulties this has now created . . . for the creation of trust in Ireland. I have no doubt that it lies fairly and squarely with the leadership of Sinn Féin which was until recently personally mixed together with the other members of the army council who sent them to Colombia in the first place and who made all the arrangements to get them back."
He rejected the proposition that the three men - James Monaghan, Martin McCauley and Niall Connolly - had gone to Colombia to advance peace in any way. Anybody "who is in any way intelligent" would agree with him.
"The great likelihood is that they were there for a different purpose, which was to impart technology in terror to the Farc guerrillas in Colombia."
While the Taoiseach had previously made comments regarding the safety of the men in the Colombian prison system, Mr McDowell said it would not now be hypocritical to send the men back to Colombia to serve their 17½-year sentences.
"There would be an expectation internationally that whatever remedies are provided for under international law or domestic law would be fully used to deal with that situation. If there is a case to be made for their extradition to Colombia and if it's lawful under Irish law, that is something which may well happen."
The men may also be pursued for any offences which may have been committed under Irish law, namely travelling on false passports. While no extradition treaty existed between Colombia and Ireland, one could be put in place.
Mr McDowell had received a provisional report from gardaí and will brief the Cabinet next Wednesday.
On Tuesday Colombian vice president Francisco Santos said his government would be seeking the men's extradition. He told The Irish Times in London Colombia would "not be satisfied" if they were prosecuted in Ireland only for passport offences.