Just who is the ultimate guardian?

Who guards our political system? The question is timely: John Major's announcement this week was an attempt to reclaim the respect his Government is losing through the sleaze issue. But by turning over the power to a judge and a committee, he was implying, rightly, that the traditional web of authorities - Downing Street, Parliament, and ultimately the Crown - have become unable to reassure the nation on their own.

Mr Major had already appealed to that traditional source of endorsement, the Cabinet Secretary. But the assurance that Sir Robin Butler was investigating the cash- for-questions allegations was not, this time, enough to dispel mistrust. Nor was the publication of his report, a fact that must give Sir Robin, as well as the Government, pause for thought.

Mr Major had also relied on another traditional source of independent authority, the Privileges Committee of the Commons - meeting, as is also traditional, in private. No good either: its Labour members concluded that a private investigation by MPs of MPs would intensify public suspicion, and walked out.

So who might stand above party politics and carry general authority? Mr Major said he had thought about a Royal Commission, but dismissed it as too cumbersome. He had thought about a Speaker's Conference. But that deals with electoral law. He had thought of turning to some of those eminent politicians who are members of the Sovereign's Privy Council. But that 'might be seen as too narrowly drawn'. He had thought of a judicial inquiry, but dismissed it, also, as too narrow.

This is no mere matter of administrative tidiness. Here we have the country's senior politician twisting about, searching vainly for some authentic and final source of authority and judgement in this matter. He is not asking a bureaucratic question, or even a moral one. He is asking a constitutional question: who polices the politicians? Who holds the ring?

And he cannot find an answer.

In the most sudden and unplanned way, the Prime Minister had run up against a question that Labour has been increasingly worried about: after 15 years, to what extent is there an independent state, standing above, and separate from, the Conservative leaders?

Once, even to pose the question would have been to invite ridicule and bewilderment. To suggest that Sir Robin was somehow compromised by being both the Prime Minister's closest mandarin adviser and Head of the Home Civil Service, would have been simply impertinent. Constitutional experts would have explained that the ministers had been loaned a machine, rather like a grand company car, and were attached to it only temporarily by the seats of their trousers.

But, to continue the analogy, the feeling has grown that they have customised the car ever more drastically for their own use. Ministers have tacked on quangos, refashioned Whitehall, changed the culture, fiddled with the brakes. Not surprisingly, this is felt most keenly by Opposition politicians watching the beast roar by.

But the evidence has accumulated: the use of public money for ministers' legal fees; the use of officials to dig up dirt on Bill Clinton; the cutting-out of the Opposition from appointments to the Privy Council, the House of Lords and quangos (all, remember, part of the state, supposedly neutral); the mingling of ministerial activities and party fund-raising; the blocking of MPs' questions because of the 'commercial confidence' required by companies taking over ever- larger swathes of public service.

Some examples are petty, others less so. But the level of mistrust on the Opposition benches should not be underestimated. Neil Kinnock, as Labour leader, never had a formal audience with the Queen, and even now Labour front-benchers feel cut off from the state. They reacted cautiously to government overtures about a joint approach to the sleaze issue. It is only going it a little to say that they no longer feel securely part of the system.

One vignette makes the point. At the end of the last election campaign, the private secretaries to the Queen and the Prime Minister sat with Sir Robin Butler watching the results come in on television. Had there been a hung parliament, they assumed they would have run seemly negotiations. But privately the Labour leadership did not trust this so-called 'golden triangle' to be impartial. They had already taken independent legal advice.

In a lecture this week Peter Hennessy, the writer who is himself about the nearest thing we have to a constitutional authority, speculated about what might have happened had that election produced a controversial result. Who would the Queen have invited to form a government? Under what circumstances would she have called another election? He concluded that there was a serious problem and suggested that Tony Blair and Paddy Ashdown get clarification before the next election.

Mr Major would be well advised to heed such warnings, for it no longer seems automatic that Labour anger about the 'Conservative state' will be cooled by office, or that Labour reformism will stop before it reaches the monarchy.

Professor Hennessy makes his suggestion as a monarchist, in the course of an argument intended to refute the Victorian writer Bagehot's characterisation of Britain as a country in which 'a republic has insinuated itself beneath the folds of a monarchy'. But the way things are going, Bagehot's republic, in which the monarch's last powers have been removed but the individual stays in post, may come to seem like a sensible compromise.

The monarchy problem and the current sleaze problem are closely connected because they both raise the question of who, if anyone, is the ultimate guardian of the system. It would clearly be convenient for Mr Major to re-establish a bipartisan approach to such questions, and the novel constitutional mechanism he has created for the sleaze inquiry is intended to achieve that.

In some areas this should be possible, in others it will not be. But one thing is sure: if Mr Major is to have any hope of turning aside the constitutional radicalism that 15 years of Conservative rule have nurtured, he will have to be radical himself. There are chilling rumours coming out of No 10 about the likely nature of Lord Nolan's sleaze-busting committee.

Officials want it to be as anonymous and silent as the Security Services Commission, with membership limited to a handful of eminent Westminster and Whitehall insiders. That, as Mr Major surely realises, would be a disaster: a buffers' inquiry would make his bad situation worse.

For the truth is, there is precious little unearned or innate authority left in the system. Mr Major could not find an answer because there isn't one. We have up to now relied on trust to make our haphazard constitution work - trust between the parties, trust in the neutrality of the state, and the general trust of voters that, most of the time, rules will be obeyed. We have come a long way under this system. But we have overstated its endless adaptability: it may well be that we are painfully jolting to the end of this unique constitutional road.