Warning: This footage shows distressing content.

This is the video police want the public to see highlighting the potentially lethal dangers of using synthetic cannabis.

It shows users vomiting and staggering like zombies after taking the drug, which has now been linked to seven deaths in Auckland this month.

Police have released CCTV footage of an incident in Auckland's CBD earlier this year when a man was violently ill - and can barely stand - after smoking synthetic cannabis.

Detective Inspector Gary Lendrum says police have released the footage to highlight the effects that synthetic cannabis has, and the significant harm it causes in communities.

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"We have grave concerns as users don't know what poisonous chemicals they are potentially putting into their bodies when they're smoking this drug," he said.

Tests conducted of the synthetic cannabis itself have shown that it can be very dangerous, with the possibility that some products can also be laced with other unknown chemicals.

Drug Foundation executive director Ross Bell has criticised the police decision to release CCTV footage of the man under the effects of synthetic cannabis, calling it "media titillation".

"My view is that serves no purpose whatsoever. It creates shame for people who have chosen to use these drugs, it doesn't educate the public at all."

Bell said the Drug Foundation has asked the police to release the results of their testing, and said it was important to note that the cause of the deaths had yet to be determined.

"We hadn't seen synthetic cannabis deaths in New Zealand before, and these products have been around for a while. So it could be well that there's a new poison or a new chemical on the market."

"The only way that we will know what it is is to have the police release any forensic testing they've had conducted... so that we all have a better understanding of what the hell is on the market right now."