Growing school rolls and teachers doing part-time work are being seen as the main reasons for a dire shortage of relief teachers.

Only 10 percent of primary school principals who responded to a survey agreed it was easy to find relief teachers this winter.

Auckland Primary Principals' Association president Helen Varney told Mike Hosking relievers are now becoming part-time workers.

"It means they are now regularly in schools, and the pool is smaller when a day-to-day reliever is needed."

LISTEN ABOVE AS HELEN VARNEY SPEAKS TO MIKE HOSKING