Labor MP Penny Sharpe earlier this year accepted a petition of more than 12,000 signatures to revoke the law giving heritage status to wild horses in Kosciuszko National Park.

She has also introduced a bill in the NSW upper house to repeal the law - championed by Deputy Premier John Barilaro - that was passed in 2018 against the advice of ecologists, international conservation groups and the RSPCA.

Mr Barilaro last year said the bill was about finding a balance between managing sensitive areas of the park and managing the population of brumbies through humane population control methods.

But Reclaim Kosci, the Invasive Species Council-led group behind the petition, argues it protects horses at the expense of the park's natural values, native plants and animals.

The petition was on Thursday debated in the lower house after its proponents rallied in Hyde Park.

Environment minister Matt Kean acknowledged one of the biggest threats to national parks were feral horses.

The government is about to appoint a community consultation committee and a scientific advisory committee, and is doing an audit of horse numbers in the national park, Mr Kean said.

The size of a sustainable population must be ascertained once these results are in, he said.

"We need to return to the science when it comes to environment policy and that is what I intend to listen to," Mr Kean said.

"We will work with the stakeholders involved to make sure we get the best result for our community and also for our natural environment."

Blue Mountains MP Trish Doyle told the chamber Labor opposed the bill when it was introduced and is committed to repealing it.

The act has put wild horses, "a beautiful animal, but nevertheless an introduced pest, above all other all other ecological, environmental and cultural values within the Kosciuszko National Park," Ms Doyle told the lower house on Thursday.

The concern is for the "environmental destruction and degradation of our national park by wild horses that will be allowed to run unchecked, causing irreversible damage to soil water, rare and threatened species and endangered ecological communities that are unique to the Kosciuszko National Park," she said.

Mr Barilaro, whose electorate includes the national park, told the chamber that his community "took me to an election and our position was endorsed at a general election".

Inner Sydney proponents of repealing the bill "live in some fantasy where they believe their view and their democracy trumps the democracy of local people that actually live and breathe the mountains, their generation and their culture," he said.

Australian Associated Press