Illegal cannabis gummies laced with spice are being sold to Britons on social media, scientists have warned.

Edibles seized by Wiltshire Police and tested by the University of Bristol revealed that buyers were at risk of consuming a “very high” level of spice, which could be up to 20 times the average dose, and possibly fatal.

Professor Chris Pudney said that many of the products tested also had significantly varied dosages of THC, the main active chemical in the cannabis plant, which did not match the description on the label.

The gummies, which are packaged to look like popular branded sweets, especially pose a threat to children, he added.

Prof Pudney told The Independent: “There's often an advertisement of the amount of THC that's present in the edibles, and what we found was that what was printed on the packet bore very little or no relation to what was actually in the edibles, and there was a lot of variability within the same packet from potentially very low to potentially very, very high [levels] of THC.

“We also found from some submissions that the drug wasn't even THC. Sometimes it's a drug called spice, which is a synthetic drug, which we primarily find in prisons, and that is a much more risky drug compared to THC.”

Prof Pudney said the gummies were heavily advertised on social media and easy for people to purchase.

“There are a lot of advertisements for this material...They'll deliver it to you either by post or by bringing it straight to you.

“It's part of a broader narrative that we see of drugs being very available and visibly available on social media.”

They also pose a serious risk to children because of their packaging, he added.

“The packaging is semi-professionally produced, often to mimic a known brand...and sometimes directly uses the name.

“I think there is that risk that if that's in the house and a very young child picks them up, they wouldn't know any different.”

Earlier this month, Wiltshire Police issued a warning to parents after discovering that cannabis-laced gummies disguised as innocent sweets were being sold around Swindon.

Inspector Joe Senior said: “These cannabis-laced gummies are designed to look like ordinary sweets, disguising them to parents and making them particularly appealing and dangerous to children and young people.

“We would urge parents to speak with their children about the risks, remain vigilant for unfamiliar sweets or packaging, and report any concerns to police."

Police said an 18-year-old man was arrested and 40 bags of cannabis-laced gummies, which looked like Fruit Pastilles, were seized.

“The packages of gummies were labelled as containing up to 1,000mg of THC, an extremely high quantity of cannabis which could be harmful if consumed, particularly by children,” police added.

Mr Senior told BBC that officers had witnessed people who had “suffered serious illnesses and even died from these gummies”.

“They simply did not contain what people thought they were going to contain.”