Online ads promoting intravenous drips that make false claims related to Covid-19 face prosecution by the state.
The Committee of Advertising Practice (CAP) says companies that breach its guidelines will be referred to the Medicines and Healthcare Products Regulatory Agency (MHRA).
Three clinics had ads banned last week after suggesting vitamin-drip therapy offered protection against the disease.
NHS England has previously criticised companies for peddling fake remedies.
Its guidelines state companies must not make direct or indirect claims IV drips can treat or prevent viral conditions such as coronavirus.
No treatments have yet been approved by the MHRA for Covid-19, meaning companies cannot make medical claims relating to it for any products.
Matt Wilson, public affairs manager at the Advertising Standards Agency (ASA), told BBC News: “We’re contacting other businesses who offer these treatments and directing them to remove any Covid-19-related claims from their websites and social-media pages.
“We’ll be monitoring to check they’re following the rules. Any that don’t will face sanctions.”
The ASA’s powers are limited to demanding ads must not be repeated.
It cannot issue its own penalties and its judgements are sometimes ignored.
By contrast, if the MHRA judges an offender to be non-compliant, they may be subject to prosecution and, if found guilty, could face an unlimited fine and/or up to six months’ imprisonment.
IV clinics, or lounges as they are sometimes called, are being set up all over the world, often promoted by celebrities.
In the UK, there are at least 17 dedicated IV lounges and 2,500 private clinics that offer IV therapy among other treatments.
Clients tend to be people aged under 35 who pay to have blends of saline, vitamins and enzymes infused directly into a vein.