Who are the terrorists talking to? We must know.

To claim that letting the security agencies find out who terrorist suspects  have been talking to is as evil as hacking down an unarmed soldier is a sign  of missing judgment.

The call, after the murder of Drummer Lee Rigby, to revive a Government Bill  that would allow the authorities to monitor the online activity of possible  terrorists has been met with a paranoid libertarianism that denies any sense  of proportion.

The familiar argument is that the excessive infringement of civil liberties  becomes a "recruiting sergeant" for terrorists. This may be true in the case  of measures such as long periods of detention without trial. But using new  technology to intercept terrorist plots doesn't recruit terrorists: it jails  them. The actual recruiting sergeants are the preachers of hate, some of  whom we cannot remove from this country because of the same failure to  distinguish rights from wrongs.

In Theresa May's foreword to the draft Data Communications Bill, the Home  Secretary warned that without action terrorists will not be caught and "no  responsible government could allow such a situation to develop unaddressed".  In which case, Nick Clegg is being irresponsible in preventing the  Government from bringing the measure forward.

We cannot ever know whether allowing law enforcement agencies to access  communications data would have prevented the murder of Lee Rigby but the  former independent reviewer of terrorism legislation, the Liberal Democrat  peer Lord Carlile of Berriew, swiftly criticised Mr Clegg for having blocked  the proposals this year. Parliament's cross-party Intelligence &  Security Committee has also accepted that "there is a serious problem that  requires action".

The web's powerful freedom cannot be inviolate when it becomes harmful -  whether in allowing children to see pornography or terrorists to plot  murder. Technological advance presents new opportunities to fight crime, but  also new means to commit it.

Law enforcement agencies rely on the communications records of suspects to  fight serious crime, though they can only access the content - as opposed to  the fact of contact with someone - with a warrant issued by the Home  Secretary. But where once communication was by landline, now a quarter of  the data that the authorities need cannot be obtained because it is in the  form of e-mails or messages on social media, and the proportion is set to  rise sharply. That is why it is necessary for the Government to require  internet companies to retain data such as e-mails for a year, just as  telephone records are retained now.

Yet this proposal was branded a "snooper's charter". Indeed, much of the  criticism has been near-hysterical. Some claimed that the measures would be  used to enforce traffic offences or illegal music downloads. The Editor of The  Spectator suggested that the main purpose of the Bill was "about giving  espionage powers to the taxman". The Director of Liberty asserted that the  measure would result in "blanket surveillance of the entire population". A  Lib Dem MP even said that "we are all suspects under this Bill".

All of these claims are absurd. The laws currently controlling access to  communications data would remain. It is only allowed for specified purposes  and must be proportionate; 99 per cent of authorisations are given to the  police and intelligence agencies, rather than other bodies. If there are  concerns about the breadth of these purposes, they can be addressed by  focusing the legislation more tightly.

But the paranoia that some display about state intrusion makes such rational  consideration impossible. Communications data isn't their only demon. Other  crime-fighting tools such as CCTV cameras and the DNA database are seen as  threats, too. This reflex opposition to intrusion trivialises - often to the  point of being dismissive - the threat of crime. To believe that the harm  caused to you by having a camera on a street corner equates to the harm  caused by a mugging is to lose proper perspective. Such attitudes blind  critics to the benefits of new technology, even though thousands of cases  are solved using it, serious crimes are prevented and victims are spared.

Of course, civil liberties must be protected but that means putting in place  the right safeguards, not dismissing contemporary realities. Our laws have  always sought to achieve a proper balance between liberty and security;  neither can trump the other.

An earlier home secretary, Sir Robert Peel, faced strident opposition,  including from within his own party, to his plans to create the Metropolitan  Police Force. Peel finally prevailed against those who thought his "blue  devils" were an attack on freedom. "Liberty", he said, "does not consist in  having your home robbed by organised gangs of thieves."

That is a truth that some misguided disciples of civil liberties might  remember today.

Christopher N Howarth