NSW Opposition Leader John Robertson has led a hike to protest against new laws that allow hunting in national parks.

Mr Robertson led a walk through Blue Mountains National Park, west of Sydney, yesterday morning, even though the park itself will be among 48 that will definitely remain closed to the hunting of feral animals, because of its proximity to an urban area.

The Labor leader was trying to make a wider point, after the coalition used its numbers in both houses of state parliament earlier this month to pass the Game and Feral Animal Control Act, brought by the Shooters' Party.

Premier Barry O'Farrell flagged shooting in 79 of the state's 799 national parks but the environment minister would technically have the power to approve shooting in more areas.

"Today's bushwalk was a show of force by a community feeling let down by Barry O'Farrell and determined to keep the Blue Mountains tranquil and pristine," Mr Robertson said in a statement.

"I was proud to walk alongside more than 150 mums, dads and kids who are horrified that their sanctuary could soon be overrun by hunters with high-powered weapons."

The government agreed to pass the Shooters' Party bill, breaking an election promise, to secure upper house votes to privatise the state's electricity generators.