For the first time in almost a decade Australia’s drugs regulator has begun court action against a supplements seller, after the online company claimed its products could help people build muscle while also treating anxiety, depression, heart damage, joint diseases, bone diseases and other ailments.

The Therapeutics Goods Administration (TGA) alleges Peptide Clinics Australia advertised prescription-only therapeutic goods including peptides on its website and other social media platforms. The online seller did not have TGA approval to state its products could treat diseases.

Peptides Australia also allegedly advertised a product called Melanotan II, a synthetic peptide which accelerates the effects of the sun, as a safe self-tanning product, when in has been found to be dangerous. It can cause vomiting and liver problems, and has been linked to cancer.

There are hundreds of known peptides, which are small proteins, and while some are harmless and can be bought over the counter, others can have significant adverse effects on the human body.

The TGA also alleges that from 6 March 2018 to around 23 November 2018, Peptides Australia misrepresented scientific information by stating that only 5% of sunscreens tested as part of a study held up to safety standards and “another 40% were said to contribute to developing skin cancer”. This information was inaccurate and misleading, and breached the advertising code, the TGA alleges.

“The harm suffered by consumers by reason of the contraventions outlined above includes serious harm and risk of serious harm to their health and safety,” court documents filed to the federal court in New South Wales.

“The use, particularly the use without appropriate medical supervision, of the advertised products carries substantial risks to human health. The public generally is also exposed to harm and/or risk of harm by the publication of misleading information about important public health issues such as healthy body image and the use of sunscreen in the prevention of skin cancer.”

Peptides Australia also allegedly misled consumers to believe use of the products was being supervised or approved by a medical practitioner through their website. Consumers also potentially suffered financial harm, the TGA said.

Guardian Australia has contacted Peptides Australia for comment.

The TGA is seeking financial penalties, as well as the removal of any other information in breach of the advertising code. Peptide Clinics Australia has already removed many of the advertisements in question. The case will be heard next year.

Associate Prof Ken Harvey, with Monash University’s school of public health and preventive medicine, described the allegations as “serious breaches of the therapeutic goods advertising code”.

“I hope this action the TGA has taken isn’t a one-off,” he said. “I am pleased the TGA has taken action on this but there are numerous other companies with equally egregious products and claims the TGA has been notified about repeatedly, but has yet to take action against. The TGA as a regulator has in the past been exceptionally lax.”