A security expert says increased national surveillance won't come cheap.

The country's being urged to take a rational approach to preventing future terrorism attacks.

But head of Security Consulting group Mosecon, Yan St-Pierre, told Mike Hosking there can be huge costs attached.

"There is always a balance between more security but it also can't be too expensive for a number of reasons and that the government understand that it is essential to provide security personal with the adequate tools."