Government moves that would further undermine open justice have been attacked by the very lawyers on whom ministers rely to support the existing system of closed courts. It’s a major setback for the security service, which persuaded justice secretary Kenneth Clarke to endorse the reforms in a green paper on justice and security published last October.

The MI5 proposals were prompted by the case of Binyam Mohamed, a British resident detained by the US at Guantanamo Bay. In response to a claim that Britain had been complicit in his rendition, detention and torture, the government agreed to settle the case and pay Mohamed compensation - said to be more that £1m - rather than disclose intelligence-related material to him and around 15 other former detainees.

To avoid this dilemma in future, the green paper proposes extending what are called closed material procedures to all civil claims, not just those involving national security. Under these procedures, ministers can withhold sensitive evidence from a party to litigation in which the government is involved. Instead, the evidence is shown to the court and to a special advocate, an independent lawyer - usually a barrister - who has to find a way of representing the other side’s interests without telling that party what the government’s evidence says.

Now, though, the special advocates have blown the whistle. In a response to the justice and security green paper signed by Angus McCullough QC and 56 other special advocates, the government’s proposals are dismissed as ‘insupportable’. McCullough is an experienced special advocate and the paper has been published on the excellent human rights blog he co-edits for his chambers, 1 Crown Office Row.

The QC’s opinion of the government’s proposals is shared by pretty well everyone who does this kind of work. More than a third of the 69 special advocates on the attorney general’s list have not done any cases at all while others have done very few. Of the third that do most of the work, all agree that, despite their efforts, closed material procedures ‘remain fundamentally unfair’.

McCullough and his colleagues say it’s one thing to argue that the unfairness and lack of transparency inherent in these procedures should be tolerated in areas such as deportation appeals and control order proceedings for reasons of national security. ‘It is quite another,’ they continue, ‘to suggest that government ministers should be endowed with a discretionary power to extend that unfairness and lack of transparency to any civil proceedings, including proceedings to which they are themselves party.

‘The introduction of such a sweeping power could be justified only by the most compelling of reasons. No such reason has been identified in the green paper and, in our view, none exists.’

What are the alternatives? First, the special advocates support the present rules of public interest immunity, under which a judge must decide whether the public interest in withholding the evidence is outweighed by the public interest in the proper administration of justice. In such cases, material excluded cannot be relied on by either side. Material that is included must be fully disclosed by the government.

The special advocates rightly dismiss the green paper’s argument that courts would be better off being able to see all the material under a closed procedure than they are with part of the evidence excluded on the grounds of public interest. As Lord Kerr, a justice of the Supreme Court, has said, ‘evidence which has been insulated from challenge may positively mislead’.

Second, they recommend consideration of arrangements in the US under which directly instructed lawyers acting for terrorist suspects are afforded a substantially greater measure of trust and confidence than their UK counterparts and can apply for security clearance. The US experience is ignored in the green paper’s section on international comparisons.

But perhaps the most depressing thing of all about the government’s green paper is its air of unreality. Understandably, security service lawyers have little experience of litigation in the outside world. So, as the special advocates point out, the green paper makes no attempt to consider the practical implications of taking a procedure designed for appeals against coercive state action - such as deportation or controls on movements and assets - and applying it to the trial of a civil claim.

How, for example, will a litigant be able to obtain funding to bring or defend a claim - either under legal aid, a conditional fee agreement, through after-the-event insurance or from a trade union - if the litigant’s solicitors cannot see the evidence needed to assess the chances of success? How can solicitors advise a client when to settle? How could an unsuccessful litigant be expected to pay the government’s costs?

It’s bad enough that I, as a journalist, would not be able to report hearings held under closed procedures or the resultant judgments, except in anodyne terms. What is much more serious is that lawyers acting for non-government parties in such cases would have no access to these decisions either.

Imagine bringing or defending a claim without being able to find out whether there is a precedent from the High Court, the Court of Appeal or the Supreme Court that may be on all fours with the facts of your case. As Dinah Rose QC asked in a lecture last November, ‘how is the development of the common law to be reconciled with the accumulation of a body of secret case law, accessible only to the government and a small group of special advocates?’

Time for ministers to think again.