Decriminalisation campaigners suggest ending cannabis arrests could go a long way towards easing the workload for the police force.

Rallies will be held outside 26 police stations around the country at 4pm today to call for a stop to all arrests involving the drug.

Campaigners say cannabis is a beneficial, safe medicinal plant which should be decriminalised.

They say they respect and support the work police do - and they could do more of it without being tied up with cannabis arrests.

"If they had more resources and more man hours, they would be able to actually help our communities more than they are doing now, with methamphetamine problems, and alcohol, which does far more damage and creates domestic violence," spokeswoman Rose Renton said.

She hoped police would support their action.

"They're well aware, more than any other group probably, of the harm the cannabis laws are bringing into our community and for our young ones."

Today's rallies would be peaceful, she added.

"We're renowned for being a relaxed group of people.

"It's about respecting the police as our law holders, and standing beside them ... we will not be in police way.

"And it could be wet, so we're suggesting green umbrellas and raincoats."

Campaigners will also be out and about in some centres gathering signatures for a petition calling for medicinal use of cannabis to be legalised.

"We're in the final weeks of that before it goes to Parliament next month," Renton said.

"There's a huge movement and final push on that."

Her teenage son Alex Renton was groundbreakingly prescribed medicinal cannabis shortly before his death last year.

She wasn't convinced by a Australian specialist in pain medicine's comments that the push for cannabis to be legalised for that purpose ignores medical findings that the drug is a poor pain reliever and can be harmful.

Dr Dilip Kapur spoke on the issue at a conference of the Australian and New Zealand College of Anaesthetists in Adelaide yesterday.

He said there was little evidence to support the use of marijuana for pain apart from personal testimonials.

"The medical evidence from trials that have been done suggests that marijuana does not work well at treating the kinds of pain we regularly encounter – from nerve damage to amputations, musculoskeletal pain and cancer pain. It comes off second best to existing drugs by a very long chalk," he said.

Rose Renton said legalising cannabis for pain relief wasn't about converting everyone who was on pharmaceuticals to it.

"What we are asking for is freedom to choose. And that's what we haven't got.

"Some bodies do not respond or react well to the pharmaceutical drugs, whereas they do respond and react well to a herb, which is what cannabis is."