The Government's legislation to permit 42 days pre-charge detention brings to the fore the wider question of civil liberties. In their response to the security threat ministers have dragged us ever closer to a society in which ancient rights are seriously damaged. I doubt this is the Government's intention, but it is the effect. It began with Iraq.

The invasion of Iraq was justified by overegging the threat of Saddam Hussein's non-existent weapons of mass destruction - perhaps that error was genuine.

But the case for war was embellished by linking the Iraqi regime to the 9/11 attacks on New York - for which there is not one shred of evidence. As we moved towards war, that misinformation was compounded by the implication that Saddam's Iraq was a clear and present danger to the United Kingdom, which plainly it was not.

These actions damaged our reputation overseas. And, at home - on the back of the threat of terror and two serious incidents in London - they foreshadowed a political climate in which civil liberties are slowly being sacrificed.

We now know that, despite repeated denials, our Government was complicit in rendition, or - to put it in plain terms - the transfer of suspects out of civilised jurisdiction to a place where they could be held without charge for a lengthy period.

Although the intention was presumably to garner information, such action is hardly in the spirit of the nation that gave the world Magna Carta, or the Parliament that gave it habeas corpus.

I don't believe that sacrifice of due process can be justified. If we are seen to defend our own values in a manner that does violence to them, then we run the risk of losing those values. Even worse, if our own standards fall, it will serve to recruit terrorists more effectively than their own propaganda could ever hope to.

That is no longer theoretical: we now have home-grown terrorists - born in Britain, not in Waziristan. Will they be encouraged or discouraged to rally to militancy if we bypass the sober rituals of law with which we are familiar?

The Government has introduced measures to protect against terrorism. These go beyond anything contemplated when Britain faced far more regular - and no less violent - assaults from the IRA. The justification of these has sometimes come close to scaremongering.

After terrorist attacks on London, Parliament doubled the time that suspects could be held without charge from 14 days to 28 days. Probably, that was justified. But soon Parliament will be asked to increase detention without charge to 42 days. To appease opposition, the Government is cobbling together face-saving compromises. If the measure is passed, it will be a pyrrhic victory that owes more to political survival than principle. Even so, it is hard to justify: pre-charge detention in Canada is 24 hours; South Africa, Germany, New Zealand and America 48 hours; Russia 5 days; and Turkey 7½ days.

There is no proof that an extended period of 42 days would have prevented past atrocities. There is no evidence it will prevent future atrocities. No example has yet been given of why the police need more than 28 days to frame a charge. This is a slippery slope. Assertions that it “might be useful” simply will not do. If we are to curtail the liberty of the individual, we must have more certainty than that.

But it is not only the case for 42 days detention that is bogus. So is the case for identity cards. They were to be voluntary. Now it is clear that they will be compulsory. Yet the Government has admitted that such cards would not have stopped the London bombers. Nor will they cut illegal immigration, since asylum-seekers have been obliged to carry ID cards for nearly eight years. Nor will they have any real impact on benefits fraud, as this is typically caused by misrepresentation of financial resources rather than by identity.

The Government has been saying, in a catchy, misleading piece of spin: “If you have nothing to hide, you have nothing to fear.” This is a demagogue's trick. We do have something to fear - the total loss of privacy to an intrusive state with authoritarian tendencies.

This is not a United Kingdom that I recognise and Parliament should not accept it.

Nor do I believe that anyone can defend another government innovation: a national identity register containing the DNA of tens of thousands of people who have never been charged with an offence. Under present legislation, DNA can be retained permanently for even minor misdemeanours, such as being drunk. A total of more than four million samples are already on the UK database - far more than in any other country. This includes tens of thousands of children, and a disproportionate number of black men. If this is accepted, it will one day go farther. This cannot be right: for me, it is all uncomfortably authoritarian.

So is a society in which the right to personal privacy is downgraded. These days a police superintendent can authorise bugging in public places. A chief constable can authorise bugging our homes or cars.

The Home Secretary can approve telephone tapping and the interception of our letters and e-mails. All of this is legal under an Act passed by the Labour Government. None of this requires - as it should - the sanction of a High Court Judge. Francis Pym once spoke of the democratic deficit of any government having too large a majority. He was right. In a Parliament with a more balanced representation, the undermining of personal privacy, lengthy detention before charge, identity cards and a DNA register would have never been passed.

I understand - and sympathise with - the complex dilemmas of security and crime that face the Government. But, while I understand their motives, their remedies are too stringent and not wise.

No one can rule out the possibility of another atrocity - but a free and open society is worth a certain amount of risk. A siege society is alien to our core instincts and - once in place - will be difficult to dismantle. It is a road down which we should not go.

Sir John Major was Prime Minister from 1990 to 1997. In 1991 the IRA tried to bomb him and his Cabinet as it met in Downing Street

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