Abuses carried out under the CIA's secret programme of extraordinary rendition are to be investigated by one of the Senate's most powerful committees, it emerged today.

The new chairman of the Senate armed services committee, the Democratic senator Carl Levin, revealed that he was "not comfortable" with the rendition system and said it was making the US less secure.

The extra-judicial programme has seen untried criminal suspects rounded up by CIA operatives in more than a dozen countries and sent to third states for interrogation. Some captives have allegedly been snatched off the streets and suffered torture in detention.

Asked whether he would investigate the renditions programme, including the secret prisons and missing detainees, Mr Levin replied: "Yes. Yes, yes and yes."

"I'm not comfortable with the system," the Financial Times reported him as saying. "I think that there's been some significant abuses which have not made us more secure but have made us less secure and have also, perhaps, cost us some real allies, as well as not producing useful information. So I think the system needs a thorough review and, as the military would say, a thorough scrubbing."

The rendition programme was first reported by the Washington Post last year. The paper said that centres, known as black sites, were set up around the world following 9/11 and that more than 100 detainees had been sent to countries such as Afghanistan, Morocco, Egypt and Jordan.

Human rights organisations also include the more than 700 people detained since 9/11 at Guantánamo Bay. A number of people have been rendered erroneously either because of cases of mistaken identity or wrong intelligence.

According to a Council of Europe report earlier this year, 14 European countries, including Britain, have allowed extraordinary rendition flights to travel through their airspace.

Amnesty International has described extraordinary renditions as a policy of "disappearances" and welcomed Mr Levin's announcement.

"It is long overdue," an Amnesty spokeswoman said. "Many aspects of the US war on terror are of concern and are questionable. There is a need for greater transparency and we need to know who has been taken and where."

The Bush administration this year revealed that the US had transferred 14 high-value al-Qaida suspects from secret CIA prisons to Guantánamo Bay. Officials are unwilling to discuss the fate of other detainees who were rounded up around the world for interrogation.

Congress has enacted legislation aimed at preventing abuses of detainees but there has been relatively little public scrutiny of the renditions system itself.

Mr Levin made his comments as he was outlining the priorities of the committee after the Democrats' gain in last week's midterm elections. The first order of business would be to change the direction of Iraq policy, he said.