© Leon Neal/AFP/Getty ImagesBinyam Mohamed: MI5 and MI6 have expressed alarm over their long-running dispute with high court judges over pressure to disclose their involvement in the abuse he suffered
Guardian contests attempt by MI5 and MI6 to ban disclosure of intelligence-related information in British courts

MI5 and MI6 will argue in a test case before the supreme court tomorrow that in future no intelligence gathered abroad, even if initially obtained through torture, should ever be disclosed in a British court.

Last year an appeal court dismissed what it described as an attempt to undermine a fundamental principle of common law: that a litigant must see and hear the evidence used against him or her.

Now the security and intelligence agencies are challenging that ruling in an unprecedented case. The Guardian, the Times, the BBC, and the human rights groups Liberty and Justice will argue before the country's most senior judges that if the agencies get their way, the right to a fair trial will be eroded, while public confidence in decisions taken by the courts will be diminished.

These principles are particularly important when allegations of official incompetence or wrongdoing are concerned, their lawyers will argue.

The case stems from demands by six British citizens and residents held in Guantánamo Bay with, they say, the connivance of MI5 and MI6. They sought documentary evidence of what British agencies knew about the US decision secretly to render them to the base, and what part they played.

Though the six have reached a compensation settlement believed to total millions of pounds, the agencies want to establish a new principle that henceforth no intelligence-related information will be disclosed in any civil or criminal case.MI5 and MI6 have already expressed alarm about their long-running dispute with high court judges over pressure to disclose evidence of their involvement in the abuse of Binyam Mohamed, a UK resident held secretly in Pakistani and Morrocan jails before being flown to Guantánamo. Judges overrode fierce objections from the former Labour foreign secretary, David Miliband, by disclosing a brief summary of CIA information passed to MI5 and MI6.

If the security and intelligence agencies got their way, then any information relevant in a civil or criminal court case could be seen by judges and prosecutors but not by defendants themselves or even by their lawyers. Instead, the material would be seen by vetted "special advocates".

The government intends to publish a green paper this year proposing new statutory legislation asking parliament to restrict intelligence evidence from being disclosed in court in future in a way judges have so far raised serious objections to.