The Greens and three festival goers will challenge NSW Police in court over plans to deny ticket-holders entry if they are singled out by sniffer dogs, even if they have no drugs.

The force warned this week that officers patrolling Above & Beyond music festival at Sydney Olympic Park on Saturday would kick out any attendants targeted by the drug-detection dogs.

“Police will exclude any person from the venue that the drug dog indicates has or who has recently had drugs on them, regardless of whether drugs are located,” Assistant Commissioner Peter Thurtell said.

“If a dog makes an indication you will be denied entry.”

Tom Raue is one of three plaintiffs planning to file an injunction in the Supreme Court on Friday to stop what has been labelled an overreach of police powers.

The 27-year-old said the often-inaccurate dog indications prompt body searches that leave punters feeling violated.

“They will strip you completely naked. They will lift up your breasts or your scrotum, make you bend over and shine a torch in all your cavities,” he said.

NSW Greens MLC David Shoebridge backed the injunction and said the police strategy violates civil liberties and could be illegal.

“It involves punishment in the absence of any offence,” he said in a statement.

“It is not a crime to have a drug dog falsely indicate you are carrying drugs. Right now people are facing the very real prospect of having their tickets torn up because of the failed drug dog program.

“We’ve got advice that there is a strong case to be made that the police do not have the power to do this.”

He claimed drug dogs made false indications 75 per cent of the time.

It’s official – see you in court tomorrow @nswpolice pic.twitter.com/pJ8xpQGSwo

— David Shoebridge (@DavidShoebridge) June 7, 2018

Police Minister Troy Grant on Thursday told parliament he’d been informed NSW Police would turn away ticket-holders identified by drug dogs with the support and agreement of Sydney Showgrounds, the licensee and event promoters.

Mr Grant said police used drugs dogs to “great effect”, deterring drug users and catching supplies.

He said no one could ever be certain of what’s in a party drug, which were causing “far too many deaths”.

Former commissioner of the Australian Border Force Roman Quaedvlieg, who spent more than three decades in drug enforcement, said he found the move “extraordinary”.

“Festival drugs are risky granted but a person can have minute drug traces from handling cash, infused into garment fabric etc,” he posted on Twitter.

Mr Quaedvlieg said the rates of positives and false positives can change depending on variables, including the drug type and concentration, how recent the contact was, the crowd, the drug density and skill of the dogs involved.

“Using an ‘indication’, as they call it, to ban entry into a social event is too much,” he said.

In 2006, then-NSW Ombudsman Bruce Barbour found drug dogs had been proven to be “ineffective” in catching dealers.

That review said dogs found drugs only 26 per cent of the time.

“Despite the best efforts of police officers, the use of drug-detection dogs has proven to be an ineffective tool for detecting drug dealers,” Mr Barbour said in the report foreword.

“Overwhelmingly, the use of drug-detection dogs has led to public searches of individuals in which no drugs were found, or to the detection of (mostly young) adults in possession of very small amounts of cannabis for personal use.

“These findings have led us to question whether the Drug Dogs Act will ever provide a fair, efficacious and cost-effective tool to target drug supply.”

NSW Police declined to comment when approached by The New Daily.

-with AAP