The government is facing renewed pressure over its refusal to disclose Britain's role in abducting terror suspects after the information tribunal ruled there was "a very strong public interest in transparency and accountability" over whether ministers actually applied their stated policy of opposing such practices.

The public interest in openness was all the greater "as ministers have had to correct earlier statements made to parliament about UK involvement" in the practice known as extraordinary rendition – the seizure of prisoners and transfer of them to places where they were likely to be abused and tortured – the tribunal has found.

However, it has ruled that evidence in Foreign Office (FCO) documents revealing the role of MI5 and MI6 must remain secret on the grounds of national security and because their disclosure would "damage international relations".

The tribunal's ruling is in response to a request by the all-party group on extraordinary rendition (APG) for intelligence documents showing how British officials were involved in the secret rendition of UK residents to Guantánamo Bay and other prisons, how the FCO may have asked John Bellinger, then the US state department legal adviser, to say Washington opposed the disclosure of CIA intelligence, and what Britain's security and intelligence agencies told the CIA about Bisher al-Rawi and Jamil el-Banna, two UK residents seized in Gambia in 2002, and sent to to Guantánamo.

Andrew Tyrie, Conservative MP for Chichester and chairman of the APG, told the Guardian on Thursday the tribunal's ruling made even more urgent the need to set up a new independent inquiry into the whole affair.

He said: "The tribunal noted the very strong public interest in transparency and accountability on the issue of rendition. However, [it] took a cautious view of the exemptions given to information relating to the security services and to international relations under FoI."

Tyrie added: "I do not dispute the importance of protecting national security and the reputation and effectiveness of our security services. However, I also believe strongly that both will best be protected by resolving the outstanding allegations about rendition so that we can draw a line under the issue and move on".

The all-party group has not decided whether to appeal against the tribunal's ruling which adopted an extremely wide interpretation of information which could be classed as American intelligence and the range of information that would harm UK relations with the US if it was disclosed.

Tyrie said: "The mixed record, so far, in obtaining the minimum essential sunlight to disinfect this issue emphasises the importance of getting to the truth through an independent judge-led inquiry. The government was right to close the Gibson inquiry [into the treatment of detainees] but it is vital that a new inquiry, learning the lessons from where Gibson fell short, is constituted as soon as possible."

During the tribunal hearing, the parliamentary group referred to inaccurate statements to the Commons by former Labour ministers, notably Jack Straw. Years later, and only after persistent questioning from some backbench MPs and journalists, government assurances were shown to be false, the tribunal heard.

In two examples, the government had to admit that the British Indian Ocean territory of Diego Garcia had been used by the US in CIA rendition flights and British soldiers had handed over to the US two men who were subsequently incarcerated in the notorious prison in Bagram, Afghanistan, Tyrie told the tribunal.

The UN special rapporteur on human rights and counter-terrorism, Ben Emmerson QC, recently stressed the need for transparency and accountability "not only to bring to justice those officials who may have participated in crimes of this kind but also in dispelling unjustified suspicions. The unjustified maintenance of secrecy, on dubious legal grounds, only delays efforts at establishing the truth.

"Refusing disclosure of key information about the alleged participation of UK officials in extraordinary rendition runs the risk of promoting impunity for state officials of the UK who may have been party to grave human rights violations," he said.

He was responding to a decision by a federal judge in the US last week to prevent Tyrie's parliamentary group seeing evidence of British involvement in the CIA's practice of extraordinary rendition.

The judge, Ricardo Urbina, said the information had to be withheld on grounds that the parliamentary body was part of a "foreign government entity". Emmerson said the decision "flies in the face of the principles of best practice for the oversight of intelligence services".