Several brands of diet and detox teas have been taken off the shelves after they were found to have contained a pharmacy-only medication.
A Consumer New Zealand investigation found that the teas contained senna, a source of sennosides, which are used to treat constipation, the organisation said in a statement.
Three Healtheries Naturally Slim teas, available in supermarkets, were removed from sale following the investigation, including Healtheries Naturally Slim Lemon Tea, Healtheries Naturally Slim Superfruit Acai and Blueberry Tea, and Healtheries Herbalax Senna Peppermint Tea.
Other teas removed from sale included Senna Klenz, which was promoted as a detox tea and sold at health food stores, and a senna "teatox" advertised by influencer and personal trainer Sera Lilly on her website fat2fitnz.co.nz.
Companies need consent from Medsafe to advertise or sell products containing senna. None of the teas had received approval prior to sale.
Chief executive Sue Chetwin said it was concerning that companies appeared to be unaware of the rules. Senna can lead to liver damage if taken for too long, she said.
"These types of products make various claims about weight loss or ‘detoxing’ but they can be little more than laxatives in disguise," Ms Chetwin said.
She advised consumers not to waste money on diet and detox teas. "There’s no good evidence these products provide any benefits and they could even do you harm."
"You don’t need to buy a pricey tea to 'detox'. Your body is already primed to get rid of toxins by itself."
In a statement, Vitaco, which owns Healtheries of New Zealand, said, "Vitaco was contacted last year by Consumer in regards to three of it's Healtheries teas which contained senna leaf."
"Following this we undertook a full investigation and review of the issue. As a result Vitaco ceased selling these teas in early November 2019. Vitaco no longer uses senna lead as an ingredient in any Healtheries products."
Advertising or selling pharmacy-only medicines, such as senna, without consent can result in a fine of up to $100,000.
But Medsafe told 1 NEWS today is not taking any further action against the companies who breached the Medicines Act at this stage.
"It's important to stress to consumers there are no longterm adverse effects anticipated from the short term use of senna (senna leaf)," Medsafe's Chris James said.
A Ministry of Health spokesperson said the agency will continue to monitor the situation and take action as needed.