A New South Wales farm trespass bill has been criticised by civil liberties organisations, environment groups and unions for turning into “a crackdown on people’s rights to protest”.

The Right to Farm Bill 2019, currently before the NSW parliament, can punish unlawful entry and disruption on “inclosed lands” with up to three years in jail, and increases the fine from $5,500 to $22,000.

The bill is aimed at stopping animal rights protests on farms, but a range of groups and MPs say the wording would outlaw civil protest on any enclosed space, including schools, hospitals, mine sites or banks.

Chris Gambian, the chief executive of the Nature Conservation Council of NSW, said the threat to protest was “hidden within this bill”.

“It includes farmers and knitting nanas protesting coal seam gas, unions on worksites, people staging a sit-in in corporate headquarters of a company, and more.

On Tuesday, the independent NSW MP Justin Field proposed an amendment that inserts a clause so it “does not apply to a person who is engaged in a genuine peaceful demonstration or protest”.

Without it, he said the new bill “massively increases penalties and introduces jail time for peaceful assembly and protest activities that have nothing to do with farming”.

Pauline Wright, the president of the NSW Civil Liberties Council, said the new law was unnecessary and the wording too broad.

“These laws, although they are expressed to be talking about people coming onto farmlands and disturbing farmers going about their business, in fact they apply to any lands that are by definition enclosed … It is a crackdown on people’s rights to protest.”

Wright said that existing laws against trespass already dealt with the issue adequately. The government had earlier increased the penalty from $550 to $5,500 in 2016.

“I can’t see the purpose of these new laws,” she said. “The existing laws already criminalise the behaviour that is targeted by this. It seems to just be grandstanding on the part of the politicians.

“We of course don’t like the notion of anyone entering on private land and acting unlawfully, and that shouldn’t be condoned. And it’s not. The law already adequately deals with that. Imposing tougher penalties won’t do anything. All the research indicates this does not act as a deterrent.”

The proposed bill would amend the existing Inclosed Lands Protection Act 1901 to create harsher penalties.

It would also add the words “or hinder” to the offence of “interfering with” business on that land.

Under the new penalty, a person would be fined $13,200 or imprisoned for a year (or both) if acting alone, and fined $22,000 and jailed for three years if with two other people or under other aggravating circumstances.

Inclosed lands are defined by the act as “any land, either public or private, inclosed or surrounded by any fence, wall or other erection, or by some natural feature …including the whole or part of any building”.

But the agriculture minister, Adam Marshall, said the bill would not affect peaceful protests, and had been mischaracterised by “minority groups”.

“This bill doesn’t impinge on anyone’s right to peacefully protest. It punishes those who break onto people’s farms to cause upset and chaos to make a point,” he said.

“This bill does not infringe on rights conferred by any other piece of legislation, including union protests. A sit-in would also not be caught by these provisions as the penalties for simple trespass remain untouched. Nor would waving placards around or protesting on public land about agriculture – in fact, that happens almost every day in Martin Place already.

“What this bill does is give police the ability to punish those who break onto a farm and impede that farming business … It addresses a real need and gaps in the law.”

On Tuesday, the bill was referred by the Animal Justice Party to an inquiry, which will report back on 21 October.

Unions NSW said it was examining the bill closely but was concerned it could inhibit the ability for unions to do their work.

Thomas Costa, the assistant secretary of Unions NSW, said it was an attempt to legislate against people’s rights to protest.

“The Liberals have a track record of trying to criminalise dissent. They think they can legislate against it and frustrate our very legitimate right to protest,” he said.

“These laws are designed to intimidate activists against taking action. Even if they pass parliament, they won’t quell activist spirit.”