A Northland Civil Defence volunteer says the reluctance of his organisation to switch on tsunami sirens is risking people's lives.

Bruce Young says response times to events, such as the recent earthquake off the East Cape, are far too slow.

LISTEN ABOVE: Civil Defence volunteer Bruce Young speaks with Larry Williams

He says as things stand, large swathes of coastal Northland and the Whangarei CBD could be washed away before a tsunami siren is sounded.

Mr Young says the authorities don't want to turn the sirens on too frequently, in case people think they're crying wolf.

"Well quite frankly I'd rather have the sirens go off six times a year, as would everyone in the community. If they go off six times a year and we have to make sure we listen to the radio to make a good decision, that's fine."

Mr Young says people believe the sirens will warn them if they're in possible danger.

But he says the directive to turn those sirens on has to pass first from the Ministry of Civil Defence and Emergency Management in Wellington, then to local councils, before Northpower is given authority to switch them on.

He says if an event takes place around the Kermadec Trench, a tsunami wave will reach New Zealand within 25 to 30 minutes - but it can take three hours to activate the sirens.