Enjoyable as it was, the Maoist ritual humiliation of bankers by the House of Commons Treasury committee raised more questions than it answered. Our elected legislators may not want to ask what responsibility they themselves bear for the economic catastrophe, but we can. And we can ask the same question about other public disasters, above all a needless and illegal war.

That's easily and specifically answered. There are 14 members of the Treasury committee, all but three of whom voted for the Iraq war in the crucial division of March 2003. All the Tories voted for the war, as did seven out of eight Labour MPs, including John McFall, who chairs the committee.

The three who voted against were the two Lib Dems - Colin Breed and Lord Thurso - and Jim Cousins, a token Labour rebel. Token is the word: these committees are closely invigilated by the whips' offices, with membership a reward for loyalty.

And of course the home secretary also voted for the war. In the Observer, Catherine Bennett has just reminded any feminists who might be pleased to see a record number of women in the cabinet that every one of them supported the war, including Jacqui Smith. She is in trouble at present, quite rightly - and there could just be a connection between her curious expenses claims and her endorsement of the war.

Whatever boasts are made about the democratisation of Iraq, the sixth anniversary of the invasion next month will be a bleak landmark in the decay of our parliamentary democracy, closely linked with the institutionalisation and professionalisation of politics over the past century. In two years comes another anniversary - the payment of MPs, which began in 1911 (all of £400 a year then). Nowadays MPs like to complain they aren't paid enough, and it has been argued that they might be better remunerated while becoming purely full-time.

And yet paying MPs has led, in a fine case of unintended consequences, to the evolution of a class of professional, albeit mediocre, politician - and we have become demonstrably much worse governed as a result. It might seem facetious or cranky to suggest that paying MPs was a mistake, but consider this: if members of parliament were not paid, we would not have gone to war in Iraq.

Since 1911, professionalisation has gathered pace. A hundred years ago, MPs weren't paid; 60 years ago they had no expenses apart from postage; 40 years ago not one MP in 10 employed a secretary or researcher. MPs will say that their work has become more onerous, but this is true only in terms of the pernicious "constituency business" to which they devote far too much time, while they devote far too little to what they should be doing - and while, frankly, they feather their nests.

The thick skin of bankers who pocket bonuses from the taxpayer has been matched by politicians, with their lavish expenses, John Lewis lists and infamous pensions that, unlike most people's, are secure against the financial calamity over which parliament has presided. Derek Conway's illicit scam was disgusting, but what's licit is almost worse.

Ordinary voters, Labour and Tory alike, have been repelled by Smith's specious "second home" arrangement. In any other business, to claim that a bedroom in your sister's house was your principal residence would look dishonest. Now Smith digs a deeper hole by telling us that she didn't actually claim the full second-home allowance - which turns out to mean that the £116,000 she received was all of £58 short of the maximum entitlement.

And parliament, far from doing a better job, does a worse job with every year that passes. That means everything from hopelessly inadequate scrutiny of bad legislation to passivity in the face of a great assault on civil liberties - including the practice of torture, as the case of Binyam Mohamed reminds us - and support for a war that most Labour MPs in their hearts didn't want.

Six years ago a loyalist who disliked the approaching war wrote in these pages that, although Tony Blair might be exaggerating the case for war, that's what governments do when wars begin. This was revealing, because it was entirely untrue. British governments have historically exaggerated the case for peace. Aberdeen hated the Crimean war that began when he was prime minister; Salisbury wasn't much keener on the Boer war; and twice in the last century we entered great wars with the deepest reluctance, on the part of the Asquith cabinet in 1914 and, more notoriously, Chamberlain's in 1939. It was parliament "speaking for England" that forced Chamberlain's hand.

What has changed over the last century is the ever-increasing strength of the executive, and the biddable servility of the Commons, a fact that can be dramatically illustrated. Since MPs were first paid in 1911, just two governments have fallen as a result of parliamentary votes: Ramsay MacDonald's first Labour government in 1924 - in any case a minority administration living on suffrance - and James Callaghan's Labour government in 1979, which had seen its Commons majority in effect evaporate.

Now go back a hundred years in the opposite direction from 1911, and recall that every British government between 1837 and 1874 fell following a Commons vote. That happened again in 1886 and 1895. Political conditions were different, and politicians drawn from a narrow elite. All the same, there really was a golden age of parliamentary government, when the Commons was the master of the ministry - rather than the other way round, as now. And that was connected with the fact that for most MPs politics was not a "job" that they lived in dread of losing. They were almost light-heartedly ready to bring down governments, and they would unquestionably never have voted for a war they didn't really believe in.

Ending the payment of MPs is perhaps too much to hope for. As it happens, payment was one of the Chartists' demands in the 1840s, all of which, from equal constituencies to manhood suffrage, were eventually met, with one exception - annual parliaments. But why not? To elect the Commons every year would encourage a much greater turnover; ordinary men and women would be able to sit for a term or two; the institutionalisation of the political class would be halted.

Here's a slogan for our age: give politics back to the people!

• Geoffrey Wheatcroft is the author of The Strange Death of Tory England wheaty@compuserve.com