The American humorist Fred Allen remarked that "a committee is a group of people who individually can do nothing, but as a group decide nothing can be done". Had Mr Allen been alive to survey the beguiling spectacle of another week in Britain's war on terror, he might have revised this judgment on the basis that it is clearly preposterously flattering to the good burghers of the intelligence and security committee.

As an American, he might have been momentarily charmed by legislative posturing in a country where the bite of the average select committee makes its church hall equivalent look like the Watergate hearings. But nothing rains on the Westminster village fete like large-scale loss of life, and it is impossible to understand how anyone can hold - when the fertiliser bomb trial has revealed the surveillance blunders that allowed two of the July 7 bombers to strike - that the ISC's sketchy report of its inquiry into the matter can remain a satisfactory last word.

Anyone, that is, bar a past master. So adept is Tony Blair at styling himself the saintly taker of unpopular yet unimpeachably right decisions that, if he eventually judges himself rich enough to take a peerage, his heraldic crest should feature a halo-sporting figure dragging a ploughshare through a lonely furrow.

"The reason people want another inquiry," he kindly explained as he dismissed the idea this week, "and I totally understand both the grief of the victims of 7/7 and their anxiety to have another inquiry, is that people want another inquiry to reach a different conclusion." If anything is indicative of Mr Blair's serial willingness to misrepresent those he serves - a willingness that amounts to little more than contempt - then it is that use of "want".

People do not "want" it to be established that mistakes were made by those in whom they have to trust to keep them safe. People do not "want" to live with any potential conclusion that lives were needlessly lost as a result of a cock-ups or arcane funding decisions. But people would prefer to think a credible body had unearthed the truth about the competence with which they are allegedly protected from the very forces of darkness Mr Blair claims surround them.

Unfortunately, under the present system of committee inquiries you will no more satisfy this eminently reasonable desire in the public than you will convince them that the PM and his chancellor have always been best friends.

When Elizabeth Filkin, the former Commons standards commissioner, granted an interview to this newspaper after she had been constructively removed from her job, she despaired of the assumption that the public are too skittish and moronic to be presented with even the sanitised conclusions of regulatory bodies. "The public are not stupid. The public look at the facts," she insisted. "They're perfectly sensible, they know perfectly well what matters and what doesn't."

Yet her dealings with the standards and privileges committee had left her concerned "as to whether there are some situations where the possibility of preferment or party influence had got in the way". Naturally Ms Filkin speaks in the measured tones of a civil servant. The less restrained among us would be surprised if the latter had ever not got in the way. In the Escher-like structure that is our system of checks and balances, committees are constructed on party lines, and their chairs appointed by the government, which can in turn prevent advisers and civil servants from appearing before them.

Say what you will about American politics, it is impossible not to feel deeply envious when you observe a congressional inquiry at full throttle. If Gordon Brown is the Atlanticist he claims to be, he cannot fail to appreciate the totemic power of these hearings in terms of preserving trust in the legislature. Think of Oliver North before the Iran-Contra hearings. The image of Alastair Campbell facing down the media committee over the Kelly affair never made quite the same impression.

Alternatively, consider Ms Filkin's claim that John Reid had intimidated witnesses to her inquiry into the forbidden use of taxpayer money for the benefit of the Labour party. "I don't think you can investigate anything too rigorously," she said, "because you're not being fair to people unless you do that." In one of those charmless ironies of British political life, Ms Filkin subsequently found herself out of a job. Mr Reid is now the home secretary.

Still, with trust such a desperate concern, and the 7/7 cock-up one of the many contentious matters from which he has kept himself so studiedly disassociated, Gordon Brown could mark his first days in No 10 with an announcement that would echo the brave new dawn of his granting independence to the Bank of England when he took control of the Treasury. Nothing less than a complete overhaul of the committee system should be promised, with greater powers of investigation and independence granted to every inquiry that would scrutinise his forthcoming glorious works.

Alas, one suspects he may shy from surrendering a great chunk of his power the minute he finally gets his hands on it, in which case merely the impression of an overhaul may be judged to suffice. Such inaction is very easily achieved, of course. He need simply leave the idea in the hands of a committee.