Viewers were misled by adverts for an anti-hair loss laser treatment, featuring sports stars, the Advertising Standards Authority has ruled.
The watchdog said Advanced Hair Studio had failed to prove that its infrared radiation treatment was effective.
Ex-England cricketer Graham Gooch and former England rugby player Austin Healey appeared in the commercials.
Advanced Hair Studio said "tens of thousands of people" across the world had benefited from its treatments.
After investigating two viewers' complaints, the Advertising Standards Authority (ASA) said the therapy's effectiveness had not been proved.
One advert showed Healey with his head in a laser device saying he had re-grown his hair with Advanced Hair Studio's laser hair therapy programme.
Members of the public were shown backing the treatment, saying "after a few months I stopped losing my hair" and "my hair loss has now stopped completely".
However, an expert told the industry watchdog it was not accepted that infrared radiation could reverse male or female hair loss.
He drew attention to "serious flaws" in a study provided by the advertiser to support its claims.
And the commercials did not make it clear that continuous treatment was needed to maintain any benefits gained from the hair loss therapy, the ASA added.
The ASA concluded: "We were concerned viewers would be misled into thinking the advertiser offered a treatment that was more effective than it actually was."
Advanced Hair Studio said Healey, Gooch and Australian cricketer Shane Warne were among 300,000 people worldwide who have taken up the laser therapy or the company's patented strand-by-strand hair replacement procedure.
It added: "Nothing in this adjudication undermines the fact that tens of thousands of people across the world continue to benefit from Advanced Hair Studio's pioneering treatment.
"We have stopped them from going bald and helped them to replace their hair - facts which no-one can dispute."
Legal Notice - 2 August 2012: This article is the subject of legal proceedings. Advanced Hair Studio claim that this article is defamatory of them and assert that a form of laser treatment which they now use, the LaserComb, has since been accepted by the ASA
in a 2012 ruling
as being proven to promote hair growth.