There are fears the teacher shortage could worsen as relief teachers leave the profession.

New Ministry of Education figures show around 3,000 relief teachers have left the profession in the last decade.

The primary teachers' union, the NZEI, has called for a complete review of the sector.

Auckland Primary Principals' Association vice-president Kyle Brewerton told Tim Dower due to salary caps, there is an assumption they work every day of the year, but it isn't the case.

He says there are times in the year like the start of the term, where staffing is very light, and usually they have nothing to work with.

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