The head of the environmental watchdog has resigned after a year of intense scrutiny, in which he referred the body to the Independent Commission Against Corruption.

Barry Buffier, 71 – once described by Opposition Leader Luke Foley as "the most powerful public servant in NSW" – served as chairman and chief executive of the NSW Environment Protection Authority since 2012.

EPA chief Barry Buffier is set to leave the authority on January 8. Credit:Max Mason Hubers MMH

This year, a Fairfax Media investigation revealed significant problems with the way the EPA policed illegal asbestos dumpers and questionable policies around land contamination.

Asked about Mr Buffier's main achievements on Monday, Environment Minister Gabrielle Upton referred to his "significant career in the public sector", thanked him and wished him well in retirement.