Washington has criticised a Council of Europe report on alleged US secret prisons inside Europe, saying it was full of allegations, but thin on facts.
CIA flights have landed in European countries, Mr Marty says
Poland and Romania rejected the fresh claims that they hosted the prisons, while the UK, named as a CIA stopover, said the report contained nothing new.
The report was prepared by a Swiss senator for the Council of Europe, the continent's human rights watchdog.
It said 14 European states colluded with the CIA on secret flights.
Under the CIA policy of rendition, prisoners are moved to third countries for interrogation. There have been allegations some were tortured.
The US admits to picking up terrorism suspects but denies sending them to nations to face torture.
The report by Swiss Senator Dick Marty follows a seven-month inquiry.
It began in November amid a political outcry over media allegations of the existence of CIA detention centres in eastern Europe.
Mr Marty examined air traffic logs, satellite images and the accounts of those who said they had been abducted.
He identified a "spider's web" of US rendition flights and landing points around the world.
And although he said the US must bear responsibility for the flights, he concluded that the programme could operate only with "the intentional or grossly negligent collusion of the European partners".
He said that Spain, Turkey, Germany and Cyprus provided "staging posts" for rendition operations, while the UK, Portugal, Ireland and Greece were "stop-off points".
The report also says Italy, Sweden, Macedonia and Bosnia allowed the abduction of residents from their soil.
The most serious charges are levelled at Poland and Romania, where Mr Marty says there is enough evidence to support suspicions that CIA secret prisons were established.
The report triggered a wave of angry denials from the European countries involved, who called the findings speculation not based on facts.
In London, UK Prime Minister Tony Blair said the report "added absolutely nothing new whatever to the information we have".
US State Department spokesman Sean McCormack described the report as "a rehash of the previous efforts," saying that Washington was "disappointed in the tone and the content of it".
The BBC's security correspondent, Frank Gardner, says that while the report makes uncomfortable reading for many European countries, the Council of Europe has been hampered by its lack of investigative powers.
The evidence in the report is largely circumstantial, our correspondent says, and proving many of the allegations, such as the existence of so-called "black sites", is beyond the council's powers.
The report is intended to wake up Europe's conscience to get national parliaments to investigate properly, our correspondent concludes.
"Governments have a duty to carry out serious, transparent investigations" of these allegations, Mr Marty said after the publication of the report.
"These states could have established the truth long ago - they did not. They now have an obligation to do so," he added.
Mr Marty's report is due to be adopted by the full parliamentary assembly of the council later this month.
Media allegations on CIA jails broke last November, when the Washington Post newspaper said the intelligence agency had been running facilities in eastern Europe, Afghanistan and Thailand.
It said more than 100 people had been sent to facilities known as "black sites" since they were set up following the 11 September 2001 attacks.
European media reports have since alleged that the CIA has used several European airports for its programme of "extraordinary renditions".
Under the highly secretive process, US intelligence agencies send terror suspects for interrogation by security officials in other countries, where they have no legal protection or rights under American law.