Per Stig Moeller, Denmark's foreign minister, said: "There is evidence in this film which I had not seen before which shows that the Americans are using private airplanes as government airplanes."

'Unaccepatable'

Lars Emil Johansen, one of Greenland's two representatives in the Danish parliament, demanded an in-depth investigation, saying he  did not have confidence in the Danish government, a long-time ally of the United States, to shed any light on the affair.

Moeller said: "It is clear that that is unacceptable, and we are going to talk to the Americans about this.

"We can say to the Americans that they have made commitments [to  respect international aviation conventions] which they are not  apparently keeping. And we would dearly like explanations on this point.

"Neither Danish airspace nor the airspace of Greenland can be used in violation of these conventions."

Last year the centrist and left-wing parties in parliament demanded an independent inquiry into the CIA's use of Danish airspace.

However, the liberal-conservative government and its far-right ally, the Danish People's Party, refused the request.

Figures from the civil aviation authority in Greenland show that a third of 35 private planes operated on a CIA account and suspected of being involved in illegal rendition flights, landed at the  Narsarsuaq airport in southern Greenland.

Between the end of 2001 and 2005 the CIA-operated planes carried out more than a thousand flights involving European airports, most  of them logistical.

But in the absence of any proper European control the only provisional figures come from an account published  by Claudio Fava, the European parliament rapporteur, last year.

Greenland is an offshore Danish territory.