A popular Australian activewear brand has been fined for implying its "anti-virus" leggings and tops are effective at protecting wearers against the coronavirus, health officials said.

Lorna Jane was fined almost Aus$40,000 (US$28,000) over claims on its website that "anti-virus activewear" protects from infectious diseases and for implying it was effective against COVID-19, the Therapeutic Goods Administration said in a statement on Friday.

"This kind of advertising could have detrimental consequences for the Australian community, creating a false sense of security and leading people to be less vigilant about hygiene and social distancing," Department of Health Deputy Secretary John Skerritt said.

The website mentioned COVID-19 alongside a description of a "non-toxic mist" that it claimed creates a "permanent, chemical-free shield" that protects against infectious diseases.

The firm has since re-branded the clothing "anti-bacterial" and said in a statement it never meant to claim the garments would fully protect wearers but instead provide "an added protection like hand sanitiser but for the clothes you wear".

"We are not trying to profiteer in any way on the fear around COVID-19," the statement said.

The fine follows a similar punishment handed to Australian celebrity chef Pete Evans after promoting a "light machine" that he claimed earlier this year could help treat coronavirus.

Most of Australia's regions have been successful in coping with the virus but an outbreak in the second-biggest city of Melbourne is threatening to derail the recovery, with the city recently returned to lockdown and its outbreak spreading to parts of Sydney.