Department of Immigration sources have claimed there is a large and growing problem of young adult Afghan asylum seekers claiming to be minors in order to benefit from expedited processing of their asylum claims and transfer to mainland Australia, with men in their mid-20s and older passing themselves off as minors and married couples purporting to be siblings.

The problem is now serious enough that Immigration is looking at ways to strengthen its age-checking system.

However, refugee lawyers have slammed the claims as “an old and discredited myth” that had been persistently shown to be false.

According to information provided at Senate Estimates hearings last week by the Department of Immigration, there are presently 112 unaccompanied minors on Christmas Island and 90 accompanied children.

One source who contacted Crikey claimed up to 70% of minors being transferred to Australia in the now-weekly charter flights from Christmas Island are in fact adults, and that adult Afghans who have successfully applied for asylum are being placed in Australian schools. Crikey understands from several sources that some high school principals have complained about the age of some “teenage” refugees placed in them.

Another source said older asylum seekers and people smugglers encouraged younger applicants to claim to be minors in what is an increasingly systemic problem.

In the absence of documentation, verifying the age of asylum seekers is difficult, and is a worldwide problem for governments dealing with refugees. Bone-density scanning — in which a person’s wrist is subject to an MRI — is used in elite sports to verify athlete’s ages, and is also used by the AFP to verify the ages of people they intend to charge with people smuggling or illegal fishing. However, it is an expensive process, and it has a margin of error of up to five years.

Immigration department spokesman Sandi Logan told Crikey: “The issue of age determination is often complex, with many clients who arrive as Irregular Maritime Arrivals presenting with no proof of identity and often not being able to provide a date or even a year of birth.

“In these circumstances the department works with clients through several interviews to determine the most likely age of the client. The department stresses the importance of being honest throughout these interview processes, and the consequences of lying, and our officers will challenge claims where they believe these to be false.”

But Logan went on to say: “Because of the challenging nature of age determination, the department is in the process of developing enhanced policy in this area and in that context providing more robust guidance for departmental decision makers. The department is always looking for ways to strengthen policies and technologies in this area to support decision makers.”

However, Logan also dismissed some of the allegations. The department was unaware of cases of married couples posing as siblings, he said, and had no knowledge of adults being placed in schools. And while minors and families are prioritised for the processing of applications, “in practice the difference in processing times is not marked”.

David Manne, of the Refugee and Immigration Legal Centre, which has regularly acted for unaccompanied minors for a decade and has extensive experience representing Christmas Island detainees, says the claims are “lazy, unsubstantiated rumours” and there is no evidence of any systematic ploy by asylum seekers claiming to be minors.

“In my experience the vast, vast majority of people who come here as unaccompanied minors are found to be so,” Manne said. He also points out that nearly all asylum seekers claiming to be minors were found to be legitimate refugees under the Howard government and the present government.

“This reflects an institutional paranoia that first arose in the Ruddock era, that unaccompanied minors were being used as ‘anchors’, because families of minors are a priority category,” Manne said. “The process of using oral evidence, and more rarely written evidence, to assess credibility has shown there has never been any evidence for it.

“The people circulating these claims are doing so knowing that they’re not supported by the facts and that they further harm children who’ve already suffered enough.”

Crikey asked ASIO to comment on the issue of security checks for minors. They were unable to respond by deadline.