Updated 1:11pm: A civil liberties campaigner says home detention can still be effective, monitoring bracelets just need to be made more secure.

At Kiwicon's conference in Wellington computer hacker William Turner showed a way to get around the electronic monitoring devices, using the cellphone network.

Tech Liberties spokesman Thomas Beagle says the monitoring of bracelet security can be improved.

He says they can be improved.

A better system just needs to be designed, and this particular hack doesn't undermine home detention as a whole.

Labour's Kelvin Davis says the issues are serious and need to be fixed as soon as possible.