One hundred and sixty-seven years ago, a man who was soon to become a Conservative prime minister said: ‘The duty of an opposition is, very simply, to oppose everything and propose nothing.’

Of course, every opposition in recent history has grabbed the chance to cause trouble for the government by opposing everything that ministers put forward – even if it is right. But some issues are too important to be played with in this way. The decision this week on 42 days pre-charge detention is undoubtedly one of them.

It was disappointing to read former prime minister John Major’s intervention in the papers last week. Leaving aside his disingenuous references to Magna Carta, there are three major considerations as to why the threat we face today from al-Qaeda-inspired extremism is of a different order to that he led the nation against in the 1990s – that of the IRA.

First, as the trial of Khalid Sheikh Mohammed in the United States has once again shown, we are dealing today with individuals who do not aim just to end others’ lives, but also wish to martyr themselves. Their terrorist techniques are not predicated on their own survival, or any form of propaganda.

Second, the level of sophisticated technology being employed is a world apart from the single computer and handful of floppy disks involved in the last IRA atrocity. Recent al-Qaeda plots have involved 400 computers, 8,000 disks and multiple identities as well as crossing numerous jurisdictions across the world – not simply the two countries of the UK and Ireland relevant to the IRA. It is risible to even think of granting a suspected terrorist bail in such circumstances.

Third, in three cases we have come close to needing every one of the 28 days currently permitted for pre-charge detention to be able to accuse suspected terrorists with a charge that would stick.

The argument that we are going much further than other countries when it comes to pre-charge detention has frequently been raised – but in truth, these comparisons are misleading. In this country a judge needs to authorise any detention beyond just 48 hours, and no other European country has the same charging process or threshold tests that we have. Detention in some other countries can last months – if not longer. In France, for instance, it is possible for a suspect to be detained by an examining magistrate for four years while any investigation continues, before charges are brought.

This is a highly charged debate. But I do feel that there is a degree of dishonesty from those who oppose extending pre-charge detention, but who are at the same time quite happy to advocate holding the same individuals, without the additional safeguards offered in the new counter terrorism bill, by offering a lesser charge which would allow investigators to continue holding the suspect beyond 28 days. In other words, those who would happily find a way around the present cut-off but would rather not say so, or vote openly to do so.

John Major argued in the papers that our liberties are worth ‘a certain amount of risk’. But the degree of risk today is an order of magnitude greater than it ever was with the IRA. We have to talk, when it comes to these planned atrocities, about prevention and not just about prosecution – precisely because the level of carnage which results from al-Qaeda inspired attacks is so great.

It is not the ‘siege society’ which Major warned of that we should fear, but refusing to take the measures necessary for our security. Such a failure to protect the public would not be forgotten or forgiven.

It is time for Labour ‘rebels’, Liberal Democrats and the Conservatives to stop playing politics over the proposal to help deal with those who want to bring us to our knees, and give the police the space and time they need to do their job properly. David Cameron in particular needs to prove that things have changed for the Tories since 1841, when Lord Derby tried to prove that politics was just a game.

Terrorism is most surely not a game – it is a matter of life and death for all of us.