Swiss Senator Dick Marty, leading an inquiry on behalf of the pan-European human rights watchdog, said in a report earlier this month that the CIA ran secret prisons in Poland and Romania -- with the knowledge of several local politicians -- to interrogate key terrorism suspects after the September 11, 2001, attacks.
The 10-member Romanian delegation said in a statement that it had decided to take no further part in the assembly's activities until Marty visits Romania "to check the so-called information and proofs that represented the basis for the incrimination."
The statement said Romania had not hosted "any sites under other states' jurisdiction" or reached any agreement that would allow such detention centers to be set up.
It described Marty's approach as "tendentious," and said it could jeopardize the credibility of the Parliamentary Assembly itself.
Romanian and Polish parliamentarians sharply criticized Marty in a June 27 debate, saying he failed to provide a single piece of hard evidence to back up his report.
The Romanian pullout is a symbolic gesture, as the parliamentary assembly has no executive powers.
Marty traveled to Bucharest in 2005, at the beginning of his investigation, but turned down recent invitations by the Romanian authorities, saying he did not want to be manipulated by them.
(with agency reports)