Hundreds of Australians could have had their identity stolen as part of a scam targeting the Medicare system, Senate estimates has heard.

There have been 369 cases of potential identity theft in the two years to June 2015, prompting the establishment of a police strike force to investigate whether the personal information of customers had been accessed and altered to obtain the sham payments.

No confirmation on any cases has been given by the Department of Human Services.

Appearing in front of a Senate committee last night, the Department's Mark Withnell also failed to provide a figure for potential losses suffered by both affected Medicare customers and the Federal Government.

Mr Withnell said even an estimated figure would be "reasonably meaningless".

"If there was money taken, it would have been from the government as payments," he said.

"Until we've finished the investigations into each of those matters, we can't determine a final figure."

The questioning was led by Labor senator Doug Cameron, who earlier this year quizzed former Human Services Minister Marise Payne on the scam seeing Medicare rebates diverted to fraudulent bank accounts.

The Department told Senator Cameron earlier this month a total of $30,550 had been identified as debts as a result of the scam.

Correspondence further stated the scam was conducted through Medicare's online claims system, which only accounted for 0.09 per cent of the 370 million claims made annually.