Federal Environment Minister Josh Frydenberg has given his approval to the NSW government's plan to protect wild horses in the Kosciuszko National Park despite labelling them "a bit of a pest" just days ago.

Mr Frydenberg had sought advice from his department about the Berejiklian government's move to give protection to "heritage horses" in NSW's biggest national park.

That plan reversed a 2016 draft strategy recommending numbers be cut - by lethal and other means - by 90 per cent to 600 in 20 years' time.

Brumbies take to the hoof on grasslands near Kiandra in the Snowy Mountains. Credit:Nick Moir

Despite last week saying the brumbies were "creating great damage to parts of that national park", and that "we want to see our flora and our fauna protected”, Mr Frydenberg changed his mind after "constructive conversations with members of the NSW government".