The Berejiklian government is accused of stalling on previous Coalition promises to seek global recognition for the Royal National Park because it plans a possible motorway extension through the reserve.

Greens NSW have obtained a May 2016 report commissioned by the Office of Heritage and Environment that recommended the government begin a scoping study in time for a world conservation congress later that year in Hawaii. It is not clear if any such study was done.

Sydney's Royal National Park was promoted as a possible World Heritage site. Credit:Jacqui Taffel

The prospect of a nomination for "Nasho" – the 16,000-hectare park to Sydney's south that in 1879 became is the world's second national park – had been touted by several Coalition environment ministers, starting with Robyn Parker.

"There is tremendous public support for World Heritage listing and the NSW government will be asking for Commonwealth assistance to prepare a nomination," Ms Parker said in a media release in September 2013.