Many EU nations were aware that the CIA used their territory for the transfer or detention of terror suspects, a draft European parliament report says.
US officials did not deny the "rendition" policy, the report says
The report follows months of investigation by a special committee of MEPs led by an Italian, Claudio Fava.
"Many governments co-operated passively or actively (with the CIA)," said Mr Fava, quoted by AFP news agency.
He accused top EU officials including foreign policy chief Javier Solana of failing to give full details to MEPs.
The report echoed allegations made in June by the Council of Europe - Europe's leading human rights watchdog - that European states were complicit in illegal CIA operations as part of the US-led "war on terror".
US President George W Bush admitted in September that the CIA had used prisons abroad for the secret detention of terror suspects, but he did not specify where the prisons were.
He insisted the suspects had not been tortured.
The draft report says several EU governments were aware of the CIA's secret detention and transfer of terror suspects.
It further accuses governments and top EU officials of failing to co-operate fully with the European parliament's investigation.
Mr Solana's evidence to the inquiry contained "omissions and denials", the draft report says.
And EU anti-terror co-ordinator Gijs de Vries was also criticised over evidence he had given.
Mr Fava's report singled out the governments of Poland and Romania of failing to co-operate with the investigation.
Both countries have strongly denied media reports that they tolerated secret CIA detention centres on their territory.
The report says the US government had first informed EU member states in 2005 that it was using their territory to transfer terror suspects.
Over the course of three meetings with EU officials, "the Americans spoke in an explicit manner about the transfer system as a method in the fight against terrorism", Mr Fava told AFP.
The report speaks of at least 18 suspected CIA "extraordinary renditions" of terror suspects - the term used for transfers to third countries for interrogation.
Mr Masri says he was abducted and held illegally in US detention
They included the cases of a German, Khaled el-Masri - allegedly abducted in Macedonia and then detained in Afghanistan - and Egyptian former imam Abu Omar, allegedly kidnapped by CIA agents in Milan.
On Tuesday, a US court began to hear an appeal from Mr Masri after he lost an earlier lawsuit demanding damages and an apology from the US government.
Mr Fava cited at least 1,245 overflights or stopovers by CIA planes in Europe - some of which he said were probably prisoner transfers.
His investigation was launched after press reports last year claiming the US operated secret prisons in some EU states and had used others as staging posts to transfer terror suspects.
The draft report urges the countries named within it to launch their own investigations into whether they violated EU human rights law, the Associated Press news agency says.