Leading article: Parliament should be the ultimate authority

The private member's Bill that comes before the Commons for its second reading today hardly rejoices in the snappiest of titles. But the Armed Forces (parliamentary approval for participation in armed conflict) Bill, tabled by Clare Short MP, has an objective that is both clear and laudable. It would require the prime minister of the day to seek parliamentary approval for the dispatch of British troops and for the declaration of war.

There is no need to look far for the genesis of this Bill. As an opponent of the Iraq war - whose resignation from the Cabinet, alas, came too late to exert maximum political effect - Ms Short wants to ensure no government can take this country to war without the endorsement of MPs. She wants the voice of the people to be heard.

What this Bill will not do, of course, is what Ms Short and all who dissented from the Iraq war would surely like it to. It will not prevent the government of the day from embarking on an unwise or unpopular war. The Prime Minister gave the Commons a vote on the use of military force against Iraq, and - in the face of eloquent and authoritative opposition - he still won. A governing party with a sufficient majority, or with Opposition support, will still be able take the country to war against the better judgement of a great many British voters.

What this Bill would do, were it to become law, is to make such an eventuality more difficult. It is one thing to argue that the experience of Iraq is likely to deter this, and future, prime ministers from again committing our armed forces under similar circumstances - although we trust it will. It is quite another to have a law on the statute book that requires the approval of both Houses of Parliament before British troops are involved in military action. A debate ensures at the very least that the arguments are aired in public; a vote shows where each MP stands. It is a necessary exercise in accountability.

There may be occasions when action has to be taken immediately and approval cannot be sought in advance. In this case, the Bill requires Parliament to meet soon thereafter and be recalled if in recess. The proposed timescale is more exacting than in the United States, where Congress has 30 days to approve US military involvement retrospectively.

The terms of this Bill are stark - which is appropriate. For British troops to engage in any conflict that does not have the approval of Parliament would be unlawful. The Prime Minister would be obliged to set out not only the reasons for sending troops but the legal authority for it, the envisaged geographical area of operations and the duration. This would ensure a regular review, if, or when, the Government wanted to alter the conditions. Were such a law in force now, the Government would have had to set before Parliament new troop deployments and out-of-area transfers (such as the one to the central sector of Iraq last December) and would have had to seek a new mandate if the conflict went on for longer than envisaged. The lessons from the ill-advised and mismanaged war in Iraq ring out from this Bill loud and clear.

But it is not just the experience of Iraq that makes it so desirable that these provisions should become law. The way the separate branches of government have evolved in Britain over the past couple of decades has resulted in an imbalance of power. The Prime Minister has become a more presidential figure. The significance of Cabinet consensus has been diminished, as has the authority of Parliament. The judiciary has increasingly stepped up to fill the gap and set the boundaries of ministerial power. As well as curbing a prime minister's ability to go to war, this Bill could also help restore some authority to Parliament. That is an equally compelling reason why it should be passed.