Amnesty International is calling for a public inquiry into whether CIA planes carrying terror suspects on their way to be tortured stopped in the UK.
Amnesty says flights have landed at airports all over the UK
The human rights group says four aircraft it believes are CIA-controlled have stopped off at UK airports more than 180 times in the last five years.
Amnesty believes the planes have flown detainees, but is unsure if prisoners were on board during the UK landings.
The government says it is unaware of any US "rendition" flights since 1998.
The Amnesty report claims to trace the movement of four of the CIA's fleet of at least 26 aircraft, which it says have taken captives to illegal detention and torture in various countries.
It claims the planes stopped off at airports including Stansted, Gatwick, Luton, Glasgow International, Glasgow Prestwick, Edinburgh, Londonderry, Belfast and Oxford Brize Norton, although is not clear if they were carrying prisoners at the time.
According to Amnesty's report, a Boeing 737 passed through Glasgow airport 19 times, while a Gulfstream V executive jet, the most common type linked to rendition claims, has passed through Glasgow airport 20 times and Prestwick 36 times.
Amnesty International UK Director Kate Allen said "mounting evidence" of CIA rendition flights meant there must be an independent inquiry into "all aspects of UK involvement in these sinister practices".
"The British public requires reassurance that UK airports like Prestwick, Belfast and Stansted are not hosting planes used to transport prisoners for secret detention and torture."
She added: "We are insisting that the US administration immediately ends all renditions, that all 'rendered' prisoners are identified, allowed access to lawyers, and that American aviation companies stop turning a blind eye to what the CIA does with their planes."
Foreign Secretary Jack Straw told MPs earlier this year the government was only aware of two cases of the US requesting and being granted permission to transfer detainees via the UK, both in 1998.
The government says it has told Washington it expects it to seek permission for any rendition flights taking detainees via UK territory and airspace.
It has also said it has no record of any requests by the US to use UK airspace or airports for rendition since the 11 September 2001 attacks.
Amnesty's 41-page report, entitled Below The Radar: Secret Flights To Torture And "Disappearance", links the US practice of rendition to the torture or ill-treatment of terror suspects.
Washington has insisted it would never send detainees to places where they would be at risk of torture.
But US Secretary of State Condoleezza Rice has also insisted rendition is not unlawful, adding: "Renditions take terrorists out of action, and save lives."
The Amnesty report also has testimonies from people who have been detained.
"Amnesty have also talked to three individuals from Yemen who are believed to have been held at the CIA's own secret detention facilities," said the BBC's security correspondent Gordon Corera.
"The men describe being held by masked men with American accents who attempted to disguise their location. Based on details of their detention, Amnesty says it believes they were held in one of a handful of countries in Eastern Europe or Central Asia," he said.
Critics of rendition say European governments have consistently turned a blind eye to the practice.