The UK has become a “wild west” for people peddling experimental peptides, steroids and other substances, a leading expert has said, warning action must be taken to avoid fatalities.

Prof Channa Jayasena of Imperial College London, a consultant in reproductive endocrinology and andrology at Hammersmith and St Mary’s hospitals, said he is now encountering patients “day in, day out” who are taking experimental peptides.

He warned there are serious risks to their use, with the issue “falling between the stools” of regulatory bodies.

Many online sellers of experimental peptides tout them as part of a “wellness” regime, while anabolic steroids are pushed for their alleged impact on image and performance.

However, Jayasena said there could be catastrophic consequences. He said steroids are known to increase the risk of death threefold while there are also dangers from peptides, not least as many are made in China and are thereby not subject to standard quality controls and are at risk of contamination.

“It feels that we’re in the wild west and it feels like we’ve rapidly arrived in a situation of lawlessness when it comes to people normalising the administration of potentially very powerful and sometimes untested peptides and products that could have devastating consequences for their health,” he said.

“It’s a shocking development that I think we’re sleepwalking into.

“People are buying this stuff and injecting it into their veins. This is atrocious, and this could lead to deaths … [Peptides are] made with lots of very powerful solvents that you have to try to remove from the process to sufficient purity so as not to be dangerous,” he said.

“I do think there’s a need for a politician or someone to actually take this by the scruff of the neck because someone’s going to die.”

The warnings come as an investigation by the Guardian revealed how fitness influencers are using the social media platform Telegram to sell anabolic steroids, prescription-only medicines and unregulated experimental peptides.

Susan Backhouse, a professor of sport psychology and behavioural nutrition at Leeds Beckett University, said that, while steroid use has historically been seen as something associated with gym settings and culture, there is now a broader normalisation of enhancement across several demographics.

“Both men and women are showing increasing dissatisfaction with how their bodies look and feel, contributing to the normalisation of enhancement practices,” Backhouse said. “We are constantly exposed to before-and-after images on our feeds. That repeated exposure creates a sense of normalisation.”

Backhouse added self-experimentation is another significant concern. “Access has become incredibly easy. Someone can see an influencer promoting a product, click a link, and have that product delivered directly to their door within days,” she said.

Jayasena said action must be taken. “It’s clearly falling between stools,” he said. “We, crazily, don’t have any regulation for people confidently making medical claims who are not professionals, which really we should have,” he added, noting the MHRA, the medicines watchdog, only tackles the regulation side, while the Advertising Standards Agency is very narrow in its scope.

Layla Moran, the Liberal Democrat chair of the health select committee, also raised concerns. “We are deeply concerned that certain tech firms are uninterested in protecting people on their platforms, and that the MHRA and other agencies lack the resources to keep up in an ever-expanding game of whack-a-mole.”

The Conservative MP Luke Evans, a former GP, said he had repeatedly raised the issue of image and performance-enhancing drugs, including anabolic steroids, in parliament, noting the sale of experimental peptides is also a concern.

“We’re letting people put this stuff into their body, which we have no idea what it does or how it works, and that’s a really scary place,” he said.

Evans said the online sphere “is making things 10 times worse” and that many people using substances such as steroids would not consider themselves to be drug users.

Evans added awareness was the first step to tackling the issue. “Number one, first start talking about it; number two, get the data behind it; and number three, work out who is actually accountable for it,” he said.

A government spokesperson said: “The UK takes the illegal sale and supply of medicines and potentially harmful substances seriously. The MHRA’s criminal enforcement unit investigates suspected offences, disrupts illegal supply chains, removes unsafe or unauthorised products and brings prosecutions where appropriate.

“Under the Online Safety Act, the illegal sale of drugs is treated as a priority given the serious harm it can cause.”