Patients are bearing the brunt of the federal government's freeze on Medicare rebates as some medical practices bump up their fees.
Doctors say they are being forced to pass on costs to patients, including pensioners, because of the government's indexation freeze on the Medicare rebate that it pays when patients visit a GP.
They say they have received hardly any increase in rebates since 2012 and with a new four-year freeze on all MBS rebates beginning on Wednesday and set to remain until 2018, they are struggling to cope with rising costs.
Brett McPherson, practice manager at the Melbourne-based Collins Street Medical Centre, said he had no choice but to raise fees.
His projections, based on an inflation rate of two per cent, indicate doctors will face a 10 per cent funding shortfall by 2018 and practices that do not pass on those costs to patients will struggle to keep the doors open.
"You pay rent, you pay power, you have to buy medical supplies, you have to pay staff, you have to pay your accountants - all the normal costs of a business," he told AAP.
"Whether they do it now or the end of the year, I think there'll be a significant number of practices that have to look at (raising fees)."
He said practices in financially disadvantaged areas, that are unable to raise fees, will probably struggle to remain viable.
"The future is not bright for that kind of practice," he said.
Earlier this year the Springs Medical Centre in regional Victoria announced "significantly reduced" government support had forced it to raise its fees, including for concession card holders.
Acting opposition health spokeswoman Tanya Plibersek said the freeze would lead to higher out-of-pocket expenses for patients than the government's unpopular plan for a GP co-payment, which it scrapped this year.
A University of Sydney study, published in the Medical Journal of Australia, has estimated GPs will have to charge non-concession patients an extra $8.43 a visit by 2017-18 to make up for a 7.1 per cent drop in income.
Health Department modelling, obtained under freedom of information laws, suggests benefits for standard GP consultations will be $2.10 less by 2017-18 under the freeze, saving the budget $1.3 billion.
Health Minister Sussan Ley has refused to rule out the possibility of costs being passed on to patients, insisting her department's modelling shows changes will be minimal.
She wants the freeze lifted as soon as possible, but other savings need to be found before that can happen.
Labor introduced the freeze in its 2013-14 budget but maintains the measure was only intended to last eight months.
Shadow treasurer Chris Bowen refused on Wednesday to commit to a reversal of the freeze.