Last week’s report by the House of Commons Justice Committee on the draft Constitutional Renewal Bill draws attention to an issue of fundamental importance: whether judicial review should be excluded if and when the Attorney-General stops a criminal investigation or prosecution on national security grounds. The committee rightly objected to such an unconstitutional immunity.

Last July the Prime Minister’s Green Paper on the governance of Britain said that he “wanted to forge a new relationship between government and citizen”. In March the draft Bill was published. Unfortunately, as Professor Jeffrey Jowell stated in his evidence to the committee, this is in truth a “Constitutional Regression” Bill. The new relationship between government and citizen that it proposes is one in which the former would enjoy powers the exercise of which would be immune from legal challenge by the latter.

Clause 12 of the Bill would confer power on the Attorney-General, if she is satisfied that it is necessary to do so for the purpose of safeguarding national security, to give a direction to the director of the Serious Fraud Office (SFO) that no criminal investigation of specified matters is to take place, and to give a direction to any prosecutor that no criminal proceedings are to be instituted or continued. Clause 13(5) adds that if, in any legal proceedings, a question arises as to whether such a direction is or was necessary for the purpose of safeguarding national security, a ministerial certificate “is conclusive evidence of that fact”.

At present, the exercise of discretionary powers is subject to judicial review even if the minister acts for national security reasons. Of course, the courts will not substitute their judgment on national security for that of a minister. But the Government is required to produce some evidence to show that the decision was required by national security, and the court assesses whether the minister considered all relevant factors, ignored irrelevant factors and acted for a proper purpose and not just because the decision was convenient or avoided a political embarrassment.

In April in the Administrative Court, Lord Justice Moses and Mr Justice Sullivan concluded that the director of the SFO acted unlawfully by stopping the investigation into alleged corruption offences by BAE Systems plc in relation to a contract with Saudi Arabia. The director was concerned that if the investigation continued, Saudi Arabia would withdraw co-operation with the UK on security and intelligence matters. The court found that the director had breached the rule of law. I should declare an interest: I act for the claimants, Corner House Research and Campaign Against Arms Trade, in the director’s appeal to the House of Lords to be heard next week. Whatever the result, it cannot be right that judges should be prevented from considering the legality of such a decision to stop a criminal investigation.

Judicial review does not just serve the important purpose of enabling citizens to test the legality of a controversial decision. It also encourages the maintenance of high standards in government. Nothing concentrates the mind of a minister or an attorney-general more than the knowledge that the decision may have to be explained and justified before independent judges. The Attorney-General’s duty to report to Parliament is no substitute for judicial review. The judiciary, not other politicians, has the function of assessing whether the decision is a lawful one.

The last occasion on which the Government attempted to introduce an ouster clause to exclude judicial review was in the Asylum and Immigration (Treatment of Claimants etc) Bill 2004. The proposal to prevent judicial review in immigration cases was so outrageous a contempt of court and a violation of the rule of law that Lord Woolf, the Lord Chief Justice, said that it inevitably prompted the question “whether our freedoms can be left in hands under an unwritten constitution”. The Government backed down.

It should do so again on this occasion. In a constitutional democracy, no government should award itself unreviewable powers. It should, instead, concentrate on ensuring that all exercises of power are lawful, and accept the obligation to justify its conduct in the courts if and when challenged. If the Government persists, and forces Clause 13(5) through Parliament, it is likely to find itself fighting an even bigger legal battle. Some judges and constitutional lawyers have suggested that judicial review is now so fundamental a part of our unwritten constitution that there is an implied limitation on the sovereignty of Parliament. A statutory provision purporting to exclude judicial control would therefore be held to be unlawful. Now that would be constitutional renewal.

The author is a practising barrister at Blackstone Chambers and a Fellow of All Souls College, Oxford

Times Recommends

• The best legal yarns this Christmas
• Legal school 'earned £1m by exploiting bar course'
• Axe may fall on 5,000 more City lawyers