Two police sniffer dog operations at suburban shopping centres in Sydney in the past nine days have been criticised as heavy-handed and a waste of resources.

Police with drug-sniffing dogs were spotted at Macarthur Square shopping centre in Campbelltown in Sydney's southwest on October 2 and were also seen conducting an operation last night at Westfield Hurstville in the city's south.

A NSW Police Force spokesman confirmed an operation "targeting anti-social behaviour" was conducted yesterday in Hurstville.

"Similar operations are ongoing and will be conducted in the near future," the force said in a statement.

Sniffer dog operations at two Sydney shopping centres on the past nine days. (Supplied)

NSW police have previously told nine.com.au that drug dog operations in Sydney are "intelligence-based and focus on locations where the use and supply of illicit drugs is known to have an increased prevalence".

Greens MP David Shoebridge - who created the Sniff Off Facebook page designed to record drug dog operations - said targeting shopping centres was a waste of resources and was damaging to long-term relations between young people and the police.

"It's no coincidence that the police are lurking outside JD Sports because the drug dog program deliberately targets young people," he told nine.com.au.

"Young people are sick and tired of being under constant surveillance by the NSW police while they go about their daily lives catching public transport, seeing a band or meeting up with friends in the evening.

"Now it seems they can't even go shopping without running into police and their drug dogs."

Mr Shoebridge questioned the effectiveness of the operations at shopping centres, suggesting it would only find end-users and not traffickers.

"I'm not an expert on major drug dealers, but I have an idea they don't normally do their trade in busy shopping centres with wall-to-wall CCTV," he said.

NSW police did not immediately respond to a request for comment.

Public strip searches often coincide with drug dog operations. (Supplied)

Drug dog operations cost taxpayers an estimated minimum of $1100 per hour, based on NSW police standard operating procedures, which use drug dogs at a cost-recovery rate of $152.20 and $23.70 per hour for officers and dogs, respectively.

"For operational reasons, it is the recommendation of the Dog Unit that whilst performing drug detection duties, each drug detection dog and handler be accompanied by a minimum of six police officers," the procedures say.

"This is the recommended minimum and depending upon the area and size of the operation, it can be increased accordingly.

"For transport/railway, licencing and general warrant operations, a minimum of eight police offers be provided – for dance party operations 10 – 12 police officers should be provided."

In August, it was revealed the number of public strip searches – often associated with the use of drug dogs - increased 1879 per cent over past decade

University of NSW researchers found there had been 5483 field strip searches in 2017/18 compared to the 277 between December 2005 and November 2006.

In the four years between 2014/15 and 2017/18, strip searches in the field failed to find drugs between 62.6 per cent and 65.6 per cent of the time.

Macarthur Square declined to comment on the operation. NSW police and Westfield and have also been contacted.

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