Mr Mair said the retailers told them financial gain was their reason for selling the substance, "over and above the mental health of the community, including a large group of youth".
"Between them they have thousands of dollars of stock on hand at any one time to sell to some of the most vulnerable in our community" he said.
"They try to hide behind a law while communities like ours are suffering on a daily basis from weak legislation."
Whanganui District Health Board clinical director mental health and addiction services Frank Rawlinson said the banning of these substances had to come from government.
Dr Rawlinson said psychoactive substances were a "societal issue", and their use was "worrying".
Another consequence of the uptake of synthetic cannabis was those who were long-time users of cannabis who did not want to get into trouble, switched to the synthetic product because it was legal.
The chemical compositions of psychoactive substances were constantly changing, he said, and under the new act, any chemical manufacturing must be proven to be safe.
However, Dr Rawlinson says he sees people on an ongoing basis in a clinical setting who were suffering the effects of using the substances.
His experience was echoed by other clinicians.
