NSW public sector fraud nearly doubles

Reports of fraud within the NSW public service have nearly doubled in the past three years but why is a mystery.

More than 1070 cases - worth an estimated $10 million - were reported between 2012 and 2015.

This compares to 562 cases of fraud between 2009 and 2012, worth more than $7 million.

Exactly what has driven the surge remains unclear, the NSW Auditor-General said on Thursday.

Almost half of 102 state agencies surveyed by the Auditor-General reported fraud in the past three years.

But the full extent of public sector fraud could be much more significant, with research suggesting the number of unreported cases could be nearly triple recorded figures.