Leading civil rights and legal campaigners have reacted with astonishment to a claim by the Association of Chief Police Officers (ACPO) that, contrary to the evidence they have accrued, Britain did not allow CIA planes to use its airports to secretly transfer terrorism suspects to third countries or US-run jails.

Chief police officers released the findings of what they say is an 18-month probe on Friday evening, ensuring that response to its claims would be delayed. The director of the respected civil rights campaign Liberty, Shami Chakrabarti, accused ACPO of “spin”. She questioned whether there had in fact been any substantial investigation.

ACPO’s claims, which will be seen as giving much-needed solace to a UK government under domestic and international pressure on the sensitive issue of colluding with torture, fly in the face of a Council of Europe report also published Friday which says the United States and NATO allies secretly agreed to allow the CIA to hold terror suspects in Europe.

Ms Chakrabarti added: “Coincidentally, Liberty [simultaneously] received a written response from Chief Constable Mike Todd on behalf of ACPO refusing to commence any police investigation into the allegations.”

The Association of Chief Police Officers (ACPO) was forced to react after Liberty claimed that flights chartered by the US government through the CIA landed in British airports. The group said it was concerned that the flights were on their way to jails where suspects risked torture. It claims the CIA “extraordinary rendition” flights have flown into Britain more than 210 times since 2001.

ACPO declared: “Mr Todd has now examined all of the information available relating to this issue and has concluded that there is indeed no evidence to substantiate Liberty’s allegations.”

It went on: “There was no evidence that UK airports were used to transport people by the CIA for torture in other countries. There was nothing to substantiate the claims in the evidence supplied by Liberty.”

Liberty is furious at the statement and its timing, which seems deliberately aimed at undermining the Council of Europe’s comments – which might otherwise have made the headlines. There are allegations that ACPO worked behind the scenes with Whitehall spin doctors to undermine critics.

Ms Chakrabarti commented: “Over 18 months ago, Liberty wrote to the police expressing concern based upon credible investigations that Britain had been used as a staging post for the CIA’s programme of extraordinary rendition. We asked for a police investigation. This afternoon, Senator Dick Marty issued the Council of Europe official report finding European collusion with extraordinary rendition and blanket over-flight clearances.”

A lawyer told Ekklesia: “ACPO’s actions will appear to many to be extraordinarily cynical. This is in danger of undermining their reputation and making them look like a political toy of an embarrassed government. The contested evidence should now be put into the public arena, notwithstanding security and intelligence concerns – which should not be used as an excuse for further cover-ups.”

Article 3 of the European Convention on Human Rights categorically states: “No one shall be subjected to torture or to inhuman or degrading treatment or punishment.”

Liberty points out that while the European Convention on Human Rights gives member states the flexibility to allow for emergency situations, there is – rightly, it says – no room for compromise on the question of torture.

“The Convention’s authors had survived the Second World War, seen people liberated from concentration camps and witnessed the worst acts of barbarity. They could not contemplate a situation where torture or inhuman or degrading treatment could be justified. Neither can we”, says Liberty.

It declares: “Our Goverment is attempting to sidestep, ignore and undermine our legal and moral obligations to prevent torture. Liberty believes that by involving ourselves torture – even if we are not actually torturing people ourselves – we make a mockery of our status as a civilised country and we lose any ability to press other countries to respect human rights.”