A trial of shark nets off the north coast of NSW could last for another two years after the Turnbull government waived environment protections despite its own departmental advice.

Environment and Energy Minister Josh Frydenberg announced on Thursday the exemption for the meshing trial from the Environment Protection and Biodiversity Conservation Act will be extended to the end of October 2019.

Shark exemption: Nets ''trial'' extended for another two years. Credit:AP

In a statement, Mr Frydenberg said the extension was "due to the risk to human life from shark interactions", and to enable the continuation of research into shark mitigation measures.

"The trials will continue to assess the catch of target sharks and bycatch of the nets against SMART drumlines used in the trial area," he said, adding the NSW government would use further trials to test ways to minimise the capture and mortality of non-target animals.