A former Food and Drug Administration (FDA) commissioner has warned that all CBD added to food in the US is still illegal.

Ex-FDA chief Scott Gottlieb

Scott Gottlieb, who left the FDA in April, told CNBC that consumers must be vigilant because the quality of the product can vary widely.

He said: “A lot of it does have high concentrations of THC. When you get CBD online, a lot of times it has high concentrations of THC.”

“You can’t just put it in the food supply.

“Right now, all the CBD is illegal that’s being put into food or dietary supplements.”

There is still confusion surrounding CBD in the US. Most cannabidiol products were made legal when President Donald Trump signed legislation removing industrial hemp from the federal government’s list of controlled substances.

But the FDA still prohibits firms from adding CBD to food, drinks and supplements.

Gottlieb, who joined pharma giant Pfizer’s board of directors earlier this summer, does see the opportunities CBD presents.

He added: “I think this is going to be an opportunity going forward. But we really need to sort out the regulation.”

The FDA is clamping down on companies illegally selling CBD products that claim to prevent, diagnose, treat, or cure serious diseases such as cancer.

Last month the regulator warned CBD company Curaleaf over the firm’s unsubstantiated health claims about its products.

Officials took issue with the Massachusetts-basedfirm over its claims that CBD could be used to treat cancer, Alzheimer’s disease, opioid withdrawal, pain and pet anxiety, and more conditions and diseases.

FDA commissioner Ned Sharpless said: “Selling unapproved products with unsubstantiated therapeutic claims — such as claims that CBD products can treat serious diseases and conditions — can put patients and consumers at risk by leading them to put off important medical care.”