New laws to give police in Victoria greater power to break up protests are unnecessary and would pose a risk to free speech, a legal group has warned.

The Victorian government will attempt to pass legislation when state parliament resumes in February that would provide a wide range of circumstances in which police could remove people from a public space.

The summary offences and sentencing amendment bill proposes allowing police to move people on if they have committed an offence within a public place within the past 12 hours, are “likely to cause an undue obstruction to another person or persons or traffic”, are “impeding or attempting to impede” someone entering a property or causing a “reasonable apprehension” of violence.

The bill follows prolonged protests at drilling sites for the controversial East West Link, which would cut through the inner-north suburbs of Melbourne.

Picketers at the drill sites have regularly clashed with police, accusing officers of using unnecessary force to remove them.

Robert Clark, Victoria’s attorney general, has said the laws will allow people to protest but also crack down on unlawful behaviour.

But unions and legal groups have voiced concerns over the move, claiming it is the latest in a string of attacks by the state government upon free speech.

“This law seems to borrow from the laws in Queensland to prevent protests at the G20. It’s part of a gradual creep against free speech protection,” Hugh de Kretser, the executive director of the Human Rights Law Centre, told Guardian Australia.

“The case hasn’t been made for the new powers and there’s a real risk they’ll be used to undermine free speech,” he said.

“They give police a broad discretion to command people to leave an area based on an individual officer’s suspicion about what a person might do. This leads to a real risk of the powers being used unfairly and arbitrarily.

“The previous move-on powers had safeguards to protect protest rights but these have been removed and the grounds on which orders can be made have been expanded,” he said.

“Any restrictions on free speech and peaceful assembly need to be necessary and proportionate. Police already have a range of legal tools to arrest and charge people for trespass or breach of the peace.”

Clark’s office had not responded to a request to comment on the new laws at the time of publication.