Data from the Australian Health Policy Collaboration at Victoria University shows children's bike sales have dropped by 22 per in the past decade.
In the past 10 years, sales have dropped by 110,000 units - from 492,000 to 382,000.
University of Sydney's Professor Chris Rissel, director of the NSW Office of Preventive Health, says this is an unhealthy trend that needs to be corrected.
"The fact that children don't have bikes means that they're not likely to be riding them," the public health expert said.
He says low bike ownership is likely to have an impact on activity levels among children, which are already worryingly low.
According to estimates, 71 per cent of children and 92 per cent of those aged between 12 and 17 do not meet the recommended guidelines of three hours per day for physical activity in Australia.
"We are failing to encourage our kids to be active enough," Prof Rissel said.
The data on bike sales have been released ahead of a roundtable event of more than 30 health experts on Tuesday.
They are meeting to discuss the need for a national approach to active travel to and from school for all children
Active travel is one of 10 priority policy actions identified in a suite of policies launched in Canberra last year.
VicHealth Principal Adviser Dr Lyn Roberts says Australian children are some of the most "chauffeured" in the world and this must change.
"Two-thirds of five-year-olds and more than half of nine-year-olds are being driven to school every day," she said.
"We need a national approach to promoting active travel to and from school so that children have the opportunity to be physically active every day."
With one-quarter of children aged seven to 15 either overweight or obese, it's vital children are provided with opportunities for physical activity every day, says Rosemary Calder, director of the Australian Health Policy Collaboration.
"Despite Australia's image as a sporting, outdoor and leisure-loving nation, almost three million children and young people are not doing enough physical activity," Ms Calder said.
Greater access to safe cycle paths for families would help, Prof Rissel says.
"It's about creating more safer bike paths and we are not doing that to the extent that we need to," he said.
"If there is not a place for children and families to go then we are all going to become unhealthy land-locked people."