The State must ensure that the United States is not illegally transporting prisoners through Shannon airport, the Council of Europe's Commissioner for Human Rights, Alvaro Gil-Robles has declared, writes Mark Hennessy, Political Correspondent.
The intervention has increased pressure on the Government to inspect aircraft owned or chartered by the CIA landing at Shannon.
Backing up the Irish Human Rights Commission (IHRC), Mr Gil-Robles said he "very much welcomed" and supported its calls for "greater transparency" in the US use of Shannon.
Last month the IHRC said the Government had "a positive obligation" to ensure that prisoners were not being illegally transported, or else face the risk of breaching international human rights law.
The Council of Europe is currently investigating allegations that prisoners were taken for torture elsewhere through European airports, and that the CIA may have operated illegal prisons in countries such as Poland.
In preliminary findings last night a Swiss senator, Dick Marty, leading one of two Council of Europe investigations, said that allegations of illegal US conduct were gaining credibility.
In a letter to the president of the IHRC, former senator Maurice Manning, Mr Gil-Robles said he had "frequently maintained that states have a responsibility to ensure that their territory and facilities are not used for illicit purposes, especially not human rights violations and, even more particularly, for violations of Article 3 of the ECHR (which covers torture).
"In so far as so-called extraordinary rendition flights are concerned, states must be in a position, where there is doubt, to establish who is on board planes transiting via their airports, whether they are travelling freely or are detained, and, if the latter, under whose authority they are being transported and for what purpose."
Supporting the IHRC's call on the Government to seek the agreement of the US authorities to Shannon inspections, the commissioner said such investigations would certainly facilitate Ireland honouring its international obligations.
"Given the widespread allegations of such transfers through numerous Council of Europe countries, I very much welcome the attention the Irish Human Rights Commission is paying to this issue and support its calls for greater transparency," he said.
Equally, he said, he welcomed the Government's stated intention of co-operating fully with the inquiries of the council's secretary general, Terry Davis, and the council's parliamentary assembly led by Mr Marty.
"It is essential that the record be set straight and that, where necessary, the appropriate lessons are learnt. National human rights institutions have an important role to play in this work," he declared.
Responding last night, the Department of Foreign Affairs said the Government did not support torture, or the use of so-called "extraordinary rendition" flights to move prisoners.
"It remains the case that the United States authorities have repeated clear and explicit assurances that no prisoners have been transported through Ireland and it remains the case that there is no evidence that any prisoner has been transported through Ireland," said an official.
However, international human rights lobby groups have tracked a half-dozen aircraft owned or chartered by the CIA that have used Shannon up to 50 times over the last three years.
A number of the aircraft, including a Gulfstream jet that has become known as the "Guantanamo Bay Express", have been linked directly with carrying a number of known prisoners, including a man kidnapped at Stockholm airport.
Meanwhile, US ambassador to Ireland James Kenny is unlikely to accept an invitation from the Oireachtas Foreign Affairs Committee, chaired by Fianna Fáil TD Michael Woods, to answer the allegations.
The invitation was issued early in December, but the US State Department has been increasingly reluctant to allow its ambassadors to appear before parliamentary committees anywhere.
Founded in 1949, the Council of Europe - which is completely separate from the EU - is Europe's oldest political organisation and includes 46 countries, including 21 from central and eastern Europe.
Set up to defend human rights, parliamentary democracy and the rule of law, the council has recently acted as a human rights watchdog over Europe's post-communist democracies.