Justice Secretary Chris Grayling has insisted he is "very confident" that judges will be acting in the interests of justice if they decide to hold a major terrorism trial behind closed doors.
The Court of Appeal is considering a challenge from media organisations to orders made at the Old Bailey for the trial of two defendants, identified only as AB and CD, to be held in secret.
Counsel for the media organisations said it was the first time that an order has been obtained to conduct a trial of this kind entirely in private, with the identity of both defendants withheld and a permanent prohibition on reporting what takes place during proceedings.
Director of civil liberties body Liberty Shami Chakrabarti said the case risked setting "a very dangerous precedent".
"It is just not justice," Ms Charkabarti told BBC Radio 4's Today programme. "The dangers of this kind of process are obvious, in terms of fairness and public confidence in a decent justice system.
"This may be an enormous precedent, but this contagion of secret justice has been spreading through our legal system since before 9/11, and each time the authorities either legislate or apply to the court for further secrecy, we are told this is exceptional, and before you know it you wake up one morning and the exceptional has become routine."
Mr Grayling insisted that the question of whether all or part of the current case should be held in private was "a matter for the courts".
He told Today: "Of course, the default in our justice system should be transparency. We shouldn't see situations where large amounts of process in our court system suddenly become secret.
"But the law does - and it's not just statute law, it's also the common law - allow very rare occasions where trials or parts of trials can take place in camera, in private. This is always a matter for the judges.
"I know our senior judiciary very well, I know that they will want to protect the interests of justice, and I am very confident that if they take a decision on a very difficult matter like this, they will do so in the interests of justice.
"In this particular case, if there is really good reason, if it is in the interests of justice for the judge to decide in one way or the other, so be it.
"That is why we trust judges. That's why we have them - to take the right decisions on behalf of all of us."
A Labour member of the House of Commons Home Affairs Committee, David Winnick, called for MPs to be given a chance to debate the issue of secret trials in Parliament.
"Parliament should be very concerned indeed that the proceedings are to be held entirely in private for the first time in centuries," Mr Winnick said.
"If this goes ahead, it may well be the case that in future the argument will be made that there is justification for other cases to be so heard. I wouldn't challenge the fact that some of the evidence may be sensitive and there is an argument for some of the evidence to be taken in private, but to take the whole case in private is, to say the least, unfortunate."
But the Government's former reviewer of anti-terrorism legislation, Lord Carlile, said it was better to hold the case in private than to allow it to fold because evidence cannot be revealed in open court.
Lord Carlile told Today: "If there is enough evidence to satisfy the normal procedural test that people have committed a serious crime - as serious as terrorism endangering the lives of the public - then, if at all possible, a trial should take place and, as long as the usual processes are followed, it may very rarely have to be in private."
Lord Justice Gross, Mr Justice Simon and Mr Justice Burnett are due to give their decision on the appeal in a few days.