Antibacterial hand soaps containing triclosan – a chemical flagged as potentially dangerous – are not much better at killing germs than regular soap, researchers have said.

Triclosan has long been one of the most common ingredients in antibacterial soaps, which are used by millions of people and generate billions in sales every year, experts say.

But studies have linked it to antibiotic resistance and hormone problems, prompting a safety review by the US Food and Drug Administration (FDA).

Now a study in the Journal of Antimicrobial Chemotherapy reports that when it comes to normal hand-washing there is “no significant difference” between plain soap and antibacterial soap in terms of killing bacteria.

Triclosan became effective only after microbes had been steeped in it for nine hours, the authors found.

“At times less than six hours there was little difference between the two [soaps],” they wrote.

To evaluate triclosan’s germ-killing abilities, the team placed 20 dangerous bacteria strains, including Escherichia coli, Listeria monocytogenes and Salmonella enteritidis in petri dishes with either antibacterial or regular soap.

The samples were heated to 22C to 40C (72F to 104F) – simulating exposure to warm or hot water – for 20 seconds, the World Health Organisation standard for hand-washing.

The team then spread bacteria on the hands of 16 adults who had refrained from using antibacterial soap for at least the preceding week. They were told to wash their hands for 30 seconds using either antibacterial or regular soap and 40C water.

For all the tests the team used antibacterial soap containing 0.3% triclosan, the maximum allowed in the European Union, Canada, Australia, China and Japan, said study co-author, Min Suk Rhee, of Korea University in Seoul.

They found no “significant” difference between antibacterial and normal soap, and decided to see if soaking would yield a different outcome.

The triclosan-containing soap only “performed significantly better after nine hours of exposure”.

Consumers needed to be made aware antibacterial soaps did not guarantee germ protection.

“It should be banned to exaggerate the effectiveness of ... products which can confuse consumers,” said Min.

Several soap makers had already stopped using triclosan, he added. Only 13 of 53 antibacterial soaps studied in Korea in 2014 still contained it.