The Turnbull government has released draft management plans for the nation's marine parks that amount to an "unprecedented roll-back" of protections, a coalition of 25 environmental groups say.

The long-awaited draft plans were released on Friday and propose changes to the 3.3 million square kilometres of Australia's protected offshore regions expanded in 2012 by the Gillard government.

The area of marine parks open to fishing would jump to 80 per cent from 64 per cent now, if the changes were to pass through parliament, WWF-Australia said.

"This is a huge step backwards for marine protection," Richard Leck, WWF's head of oceans, said. "Australia used to be seen as a global leader in marine conservation. That will no longer be the case if these proposals are implemented."