The Government is right in seeking to starve terrorists of oxygen. The State must be able to deprive those who preach violence of their platforms of hate, to deport foreigners who plot terrorism, and to detain those who seek to kill innocent civilians. But this does not mean that all the Home Secretary’s latest proposals are equally deserving of support. It is not yet clear, for example, that extending detention without trial from fourteen days to three months is either necessary or proportionate. Overly repressive legislation will only create resentment and help the enemy to breathe.

The onus must now be on the police and intelligence services who are seeking greater powers to show why they are needed, and where current laws are inadequate. The police argue that the 14-day limit on holding suspects without charge is often insufficient to establish a case. Trawling for evidence is time-consuming, and heavily encrypted computer files can take far longer than 14 days to decrypt. The investigations into the events of July 7 and 21 yielded 80,000 videos of CCTV footage to be studied and 1,400 fingerprints at 160 suspected crime scenes.

Unless the timeframe is extended, there is clearly a real danger that some of the guilty could walk free. But this risk must be carefully weighed against the need to protect the innocent from unfair imprisonment. It is a large leap from fourteen days’ detention without charge to three full months.

Today’s ministers do not envisage detaining people on anything like the scale of the 1970s Northern Ireland internment, nor for indefinite periods. Nevertheless, it would be foolish to risk radicalising young Muslims by generating the same kind of resentment that drew Irish Catholics to the Provisional IRA 30 years ago.

The Home Office is alive to the problem, and has emphasised that any three-month detention would be scrutinised weekly by a district judge. It is the view of this newspaper that any extension beyond the current 14 days should be reviewed by a High Court judge, to underline the importance of the decision, and that any extension beyond a month should be regarded as extraordinary. Ministers may fear that “activist” High Court judges would unduly favour the accused. But this is unlikely if the will of Parliament is clearly expressed.

As the list of proposed counter-terrorist measures grows longer, detailed scrutiny will be vital. It is sensible, indeed urgent, to criminalise training in the use of hazardous substances for terrorist purposes, and “acts preparatory to terrorism”, as the acquittal of all but one of those accused in the “ricin plot” clearly showed. This would enable the police to intervene even if the precise details of a terrorist plot were not known. But some of the other proposed offences on the list, such as glorifying terrorism and indirectly inciting terrorism, are less convincing. Ministers are right to seek a cross-party consensus on the Counter-Terrorism Bill. Thoughtful scrutiny from all quarters is vital if the correct balance is to be struck, and seen to be struck, between liberty and security.