There's a lot of talk but still not much action on how to reduce prison numbers.

The much-needed upgrade at Waikera Prison will see an extra 650 beds, far fewer than the mega prison National had planned.

Sociologist Jarrod Gilbert told Mike Hosking the big issue is our prison muster is at capacity

"Potentially they are creating greater victims because at the moment our recidivism rate at our prisons is very high."

LISTEN ABOVE AS JARROD GILBERT SPEAKS WITH MIKE HOSKING