The Australian Government is facing its first civil compensation suit from two Indonesian children who were locked up in an adult jail while awaiting trial on people smuggling charges.

The two boys were 14 and 15 when they were taken into custody, after an asylum boat was intercepted by customs off Ashmore Reef in February last year.

They were part of the crew.

Peter O'Brien, one of the boys' lawyers, said the Australian Federal Police (AFP) relied solely on discredited and unreliable X-ray analysis to determine their ages and then charged them as adults.

The lawyer told Australia Network's Newsline: "The fundamental problem with the prosecution of this case was that they relied on what was known to be a redundant and unreliable form of technology in determining age."

Another of the boys' lawyers, Rebecca Dunlop, said the boys even provided contact details of their families in Indonesia to Australian authorities, but it was not followed up.

"It would seem that the AFP didn't make a single phone call back to the village in Indonesia to ascertain how old they were," she said.

Mr O'Brien said the boys were initially assessed by the Department of Immigration as juveniles.

Intercepted

"When the boys' boat was intercepted by Customs, they were taken into custody by the Immigration Department and transferred from Christmas Island to Darwin," he said.

As children, under Australian policy, the pair should then have been sent home.

Instead they were transferred yet again to Sydney, where they were charged with people smuggling offences and remanded in custody.

Mr O'Brien's firm decided to travel to the boys' village to collect alternative evidence to the X-ray analysis used to determine the boys' ages.

When the evidence was provided to the Office of the Commonwealth Director of Public Prosecutions, the charges against them were immediately dropped.

But in the meantime the two teenagers have spent a total of 10 months in detention in Australia, six months of that in adult facilities awaiting trial, including in Sydney's Silverwater prison.

Mr O'Brien's firm has now filed a civil compensation suit on the boys' behalf.

Other Indonesian children have suffered similar experiences in Australia and there is little doubt there will be more claims.

Victorian Legal Aid said it is already making inquiries into possible compensation suits and Mr O'Brien has other former clients who may also have cases.

"They certainly are entitled to some form of compensation," the lawyer said.

"It's hard to know in circumstances like this what it would be worth. You can't put a price for a day in custody for a child in an adult custodial facility."