It is never too late to repent. The House of Commons can still save its self-respect following the police raid on the offices of the Tory frontbencher Damian Green. Tomorrow the government will try to put off an embarrassing inquiry into how the boys in blue were admitted into Westminster without a search warrant and without the explicit permission of their Speaker. Ministers should be told to get lost.

Alas, the best pension system in Britain, a John Lewis list of household perks and an annual salary for a mere 128 days of attendance, will incline our elected eunuchs to kowtow to the executive. MPs sold their birthright to the party whips long ago.

Oh for a Michael Foot or an Enoch Powell, a parliamentarian with the gravitas and sense of history to rally the back benches. But should we care less? Despite the pomposity and trade union instincts of some unworthier members, the answer is yes.

For there is more at stake in the Green affair than the privileges of politicians. This is a story about power. Civil service mandarins and senior police are not supposed to be mere slaves of the government. Officials should be accountable to us. And if MPs defend themselves against state power, then they defend us too. The barons at Runnymede were doubtless thinking only of their selfish interests when they wrested Magna Carta from King John, but a wider constituency benefited.

As it is, few of our representatives has risen to the occasion. The nadir was reached in an exchange on Thursday when a Tory MP, Douglas Hogg, shrieked “Cover-up, cover-up”, to which a Labour backbencher, Barry Sheerman, riposted: “You are a silly man. You have a whole history of being silly in this house, you silly man.”

Gordon Brown, a historian by education, has failed his own personal Britishness test by failing to stand up for the rights of parliament. Leaks, as he well knows from his days in opposition, are the lifeblood of democracy in this secretive country. They are embarrassing for the government of the day but they usually do it no grave harm. Sometimes there is a benefit even if national security is breached. The secret service leaked details of German rearmament to Churchill in the 1930s. That really was in the public interest.

The Speaker, too, should be ashamed of letting the police conduct a fishing expedition at Westminster: it won’t do to place all the blame on his own inexperienced appointment, the serjeant at arms, Jill Pay.

The Conservatives, backed by Liberal Democrats, have noisily defended their own. But their premature triumphalism may deny them the support of Labour backbenchers who would otherwise be sympathetic to defending the rights of MPs. Pillorying the government is good sport: but it is more important to win an argument about the way the country should be run. David Cameron and his young allies have been preaching a new gospel of localism, public accountability and the separation of powers. This programme makes amends for their party’s brutal centralisation of the state under Margaret Thatcher and John Major. In Nick Herbert, the shadow justice minister, the Tories have a man who has done the intellectual spadework on making the police accountable to local elected representatives, not Whitehall. The Opposition should be singing loudly from his hymn sheet. For the interests of MPs as well as reformers of every political stripe neatly dovetail. The problem is that the police have been nationalised.

There once used to be an important distinction in this country between administrative control of the police on the one hand and “the execution of a constable’s duties” on the other. Operational matters were for the cops. The courts could even uphold an officer’s right to disobey an “unlawful” political instruction. Under Thatcher and Major that distinction was lost. Tory governments imposed ever greater responsibilities on the police, and took control of their operations under the guise of efficiency while cutting their links to elected police authorities. In return officers were well paid but politicians had the final say over senior appointments. The Conservatives duly got their just deserts: rising crime rates and inefficient bureaucrats in uniform who spent only a third of their time fighting crime.

New Labour inherited this top heavy system and added a further layer of targets and directives. Only exceptionally strong-minded, independent officers will nowadays stand up to Whitehall. Few senior policemen can call on their communities to back them against the Home Office. One chink of light was admitted, however. Tony Blair gingerly experimented with elected mayors in a few cities, chiefly the capital.

Weeks ago Boris Johnson, the blond bombshell mayor of London, forced the last Metropolitan police commissioner, Sir Ian Blair, to resign because “he had lost the confidence of the locker room and Londoners”. He disapproved of Blair for dancing to Labour’s tune, not his. Boris wants to have the powers of his New York equivalent, Mike Bloomberg, who gets to hire and fire his police commissioner. But the Met also has national security and counter-terrorism duties, so Whitehall won’t let go of the strings. Jacqui Smith, the home secretary, has the final say on appointing the capital’s police chief.

Here we have a devil’s brew. The acting Met commissioner, Sir Paul Stephenson, and Commander Bob Quick, who was responsible for the operation to arrest Green, are both applicants for the top job. Sir David Normington, the permanent secretary at the Home Office, chairs the body that will advise the home secretary on the Met chief’s appointment. Normington wanted to find the civil servant responsible for leaking information to Green, as well he might. But then this mandarin called in the police to pursue the recipient of the leaks as well as the leaker. It appears that no senior policeman had the incentive let alone the independence to out him in his place.

Why were the police involved in plugging leaks that have nothing to do with national security? Why was Green arrested not questioned? What did the police say to the serjeant at arms to gain admittance into Green’s Commons offices: did they properly inform her of her right to refuse? These are the questions MPs should be asking tomorrow.

Here are a few simple facts our tribunes of the people should have to hand. In 1989 a revision of the Official Secrets Act conceded that all run-of-the mill leaking from government should be dealt with by internal civil service inquiry. Leakers would be found and sacked. Under section 5 of the act the prosecution would have to prove any such leaks were damaging to national security. On those grounds alone no prosecution of Green would succeed. His revelations that the Commons was employing illegal immigrants and that the Home Office employed illegal immigrants in security jobs merely made the government look silly.

That is why the police employed the obscure misconduct in public office law against Green. But this statute had already been tested and found wanting in the courts only days before. It was never designed to gag journalists and MPs. The Tory politician is in elected, not public office.

The courts have also upheld the Speaker’s right to keep the precincts of the house off limits to petty agents of the law. In 1986 Thatcher’s government bullied the BBC into pulling a documentary into a secret spy satellite, Zircon, whose existence in the usual fashion had escaped financial scrutiny by parliament. A fine Labour parliamentarian, the late Robin Cook, managed to get a video and arranged a viewing for MPs in the Commons. The attorney-general sought an injunction to stop it but the application was dismissed.

These are MPs’ rights. Now they should do their duty. Tomorrow they should ignore the whips and proceed with their inquiry. Time to give the police back to the people.

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