Social restrictions on people sitting on a park bench or walking on a beach don't make biological sense according to an infectious diseases expert.
Professor Peter Collignon from the Australian National University medical school said if people stay two metres apart it should be adequate social distancing.
Professor Collignon's comments come as NSW and Victoria introduce strict social restrictions.
"You are safer outside than inside," he said. "I do not see how anyone's going to get this virus if they keep two metres away from someone and I don't see how anyone's going to get it if they sit on a park bench."
Beach parties should certainly be broken up, Professor Collignon, of the Australian National University medical school, said. But it made no sense to stop people walking on the beach, or pausing on the beach to rest.
"These are panic decisions not decisions based on data," he said.
After concern about crowds on Bondi in Sydney, beaches have been closed in some parts of the country, and stories have emerged of people being stopped by police when they attempt to walk along a beach.
In Newcastle a family were moved along by police from their trip to the beach.
Professor Collignon said extreme measures were unwarranted and risked rebellion, especially among younger people least at risk from the virus.
"My real worry is if we overdo it now we will have people particularly in 30s and 40s who will say 'stuff this'," he said. "I think this is not sustainable for six months. We have to do everything we can to minimise the spread to others, but not do things that don't even make biological sense."
Prof Collignon was speaking as Australia's total reached 4860 at 6am on Wednesday, an increase of 8 per cent on the day before, continuing the lower rate of increase seen each day for about a week.
Professor Collignon also took aim at modeling that suggests hundreds of thousands of deaths, saying the same models were used for the SARS, ebola and swine flu epidemics and had been wrong.
Australia was already seeing the "curve" flattening.
"Just like everybody else, I haven't got a crystal ball, but the current data is reassuring that what we put in place 10 days ago has substantially decreased the spread and we're not going to see an epidemic before winter. All of these additional things will make very little difference, but will cause huge social problems," he said.
He was referring to moves to stop leaving home without excuse, with hefty fines. Earlier measures, including closing pubs and restaurants, social-distancing and quarantining overseas arrivals should continue, Professor Collignon said.
Australia was highly unlikely to eliminate the virus, so must find ways to live with it in small numbers without a long lockdown.
"My view is we are going to have this probably for the next 18 months to two years because that will be the earliest that a vaccine will become available, that's my pessimistic outlook," he said.
Asked for a response, Deputy Chief Health Officer Dr Nick Coatsworth, said, "The current measures to limit gatherings are consistent with those adopted in other nations such as the United Kingdom and are necessary to prevent Australia's epidemic worsening."
Australian authorities have so far refused to release the modelling behind their decisions.
While Deputy Chief Medical Officer Paul Kelly said earlier this week that the modelling would be "unlocked" this week, he appeared to backpedal a little on Wednesday.
Asked about expectations that it would be released, he said, "I would like to clarify that we will discuss the modelling and look to make that transparent in coming days."