A provider of urgent after-hours doctors is being investigated for fraud, a Senate committee has been told.
Officials from the Health Department told senators that 28 of the top 29 claimants have been interviewed, with five providers referred to the Professional Services Review, as of Wednesday morning.
"The investigation is ongoing," first assistant secretary Simon Cotterell told the hearing in Canberra.
"One provider is being investigated for fraud. I can't give you more details on that."
Health Minister Greg Hunt last year called for an inquiry into the after-hours sector after concerns about the claiming of subsidies for call-outs, including for visits which were classified as "urgent" but pre-booked.
Also in December the minister announced changes to rebates, including not paying the top Medicare rate for trainee doctors.
From Thursday the rebate for doctors undertaking home visits falls from $129.80 to $100.
It will reduce down to $90 from January 2019.
But there will be no change to the arrangements for doctors in regional areas.
The changes follow a review by the Medicare Benefits Schedule Review Taskforce which found:
* The number of urgent after-hours services increased by 150 per cent in the five years between 2010-11 and 2015-16. Standard GP services grew by just 15 per cent.
* Benefits paid similarly rose from $90.8 million to $245.9 million over the five years.
Officials on Wednesday played down concerns the changes could lead to a rise in visits to emergency departments.
But they said they were aware of reports the National Home Doctor Service was sending letters to patients in NSW, Queensland, Tasmania and Western Australia advising them of closures.
There are other existing providers, they said.
