At the end of an ugly, fractious week in Parliament, we may pronounce the death of a gentlemen's agreement, which served as an informal guarantee of British freedom, of the balance between the interests of government and the people as well as the maintenance of procedure.

You can read its obituary in the small print of the bills published after the Queen's Speech, in the judgement from the European Court of Human Rights on the retention of DNA of more than 800,000 innocent people and in the behaviour of those involved in the Green affair - the police, the Leader of the House, Home Secretary and Mr Speaker Martin who presides like a plump Lewis Carroll absurdity, blush and bluster his only response to the corpse that lies before him.

The arrest of Damian Green would have broken every convention in the book, if indeed there were a book. Aside from the use of nine counter-terror police and the astonishing lack of a warrant - actions which, until now, were more associated with Kazakhstan than Britain - it is worth remembering two other facts: the House of Commons internet server containing all MPs' emails was plundered by the police without permission or qualm; second, as Geoffrey Robertson QC pointed out in a letter to the Times, the law they used could mean that anyone - public watchdog, policy expert, editor, journalist or MP - who willingly receives a leak from a civil servant could suffer the maximum sentence of life imprisonment.

Part of the gentlemen's agreement was that you did not dig up ancient laws to hound your political opponents or prevent scrutiny. You respected the role of opposition MPs however pestilential their activities and you did not use the guillotine to stifle debate in the House of Commons.

It seems odd now, but there was a kind of accord which meant the government and opposition tried to fashion laws which were honest, clear and workable and which, despite political differences, were never against the interests of the people.

A close look at the Coroners and Justice Bill, published with the Queen's Speech, will tell you that the government has been up to its old trick of using the cover of reform to push a surveillance agenda, in this case to 'remove barriers to effective data sharing to support improved public services and the fight against crime and terrorism'.

What that means, as Jill Kirby, director of the Centre for Policy Studies, wrote is that: 'Under the guise of strengthening the powers of the Information Commissioner, the bill will in fact reduce parliamentary scrutiny, providing ministers with a "fast-track" procedure for sharing personal data.'

Civil servants will be crawling through our personal information like an infestation of cockroaches that can never be exterminated.

The same sleight of hand is in the draft Immigration Bill; lawyers at Liberty spotted a clause that meant the police would be able to demand an ID card from those who had entered the UK - not just foreigners who are now being issued with cards, but anyone who had been abroad, even on holiday. Whether this was a jeu d'esprit to test our vigilance or simply underhand, Jacqui Smith was forced to say that it was not her intention that police should soon be demanding people's papers. But how long can we go on accepting this woman's word about what she did or didn't intend, did or didn't know?

It was a pity that she did not present the plan to build a vast state database to record and store the information from every phone call, email and internet connection. This unbelievable measure, with an estimated cost of £12bn, has been postponed, presumably until the next terror outrage or the government finds some money. Even without this proposal, I've rarely seen such unanimity in the press as to the character and motives of the Home Secretary, her department and the police. Columnists and editorials in the Daily Mail, Independent, Sun, News of the World, Mail on Sunday, Financial Times, Daily Telegraph, Sunday Times and our sister paper, the Guardian, have lost all reservation about using the term 'police state'.

Most of us spend our time these days with our heads stuck in our screens or worrying about the economy, but out there, real and important changes are taking place.

There is a new world where economic disaster is matched by the collapse of standards that were all part of the gentlemen's agreement; tolerance, respect, fairness and shared values are being vanquished by the police and by bullying, oppressive officialdom.

You see evidence in ID cards issued to foreigners, the banning notices handed to football fans in Manchester who had caused no trouble whatsoever, but were detained and forcibly bussed back to Stoke-on-Trent without seeing their match, and also in the Metropolitan Police's Form 696, which requires venues and club managers in London 'to report to the police the names, addresses, aliases and telephone numbers of performers'. More worryingly, Form 696, which was promoted by Sir Ian Blair, demands the venue define 'the ethnicity of their audience'.

Where are Jack Straw and Peter Hain, those famous campaigners against racism? Where is Harriet Harman, once a legal officer for the National Council for Civil Liberties? Well, slippery Jack was posing as another character from Alice in Wonderland at the state opening of Parliament and later that day, Harriet squirmed on Newsnight while trying to avoid backing the Speaker.

The Damian Green affair highlights serious worries about the police. How far did they deceive the Commons officials about the warrant? What precisely did they say to Jill Pay, the hapless Serjeant at Arms? And - crucially - were ministers involved in the arrest? We need to know the answers; delays to the inquiry promised by Harman are unacceptable.

At the heart of this matter is the politicisation of the police. Are they too willing to do the government's bidding? Was Boris Johnson, chairman of the Metropolitan Police Authority, guilty of unacceptable interference, as a former senior policeman, Andy Hayman, alleges? My feeling is that the arrest of Green and seizing of material may trump any concerns about mayoral protocol, but Hayman is right to talk about the importance of having an independent police force.

If Lord Mandelson's sinuous body language and sublime containment are anything to go by, next year may bring a general election that will decide how we are governed and whether the slide into a truly frightening police-database state will continue. The Conservatives shows signs of understanding the scope of the problem - Dominic Grieve (shadow Home Secretary and Attorney General), Edward Garnier (shadow Minister for Justice), Damian Green (immigration) and David Davis have raised the alarm very effectively , but there is still a feeling that the shots of other frontbenchers, notably Cameron, Osborne and Gove, are not quite reaching the boundary. With all the support in the press, the Tories now need to show the moral and intellectual leadership to restore good government and decide how to replace the gentlemen's agreement.

After the past 10 days, many must be convinced of the need for a Bill of Rights (but not responsibilities!) with entrenched privacy laws. I am for a written constitution too, but that issue is for another time. Whether we have an election or not, it is clear that we will have to fight tooth and nail to preserve our free society in 2009. The cross-party Convention on Modern Liberty, called for 28 February 2009, will be the start of something that no politician - even Jacqui Smith - will be able to ignore.