Australians could face the introduction of a GP co-payment by "stealth" as fewer practices are predicted to offer free "bulk-billing" services because of budget measures, doctors warn.

The budget made no changes to a freeze in Medicare rebate increases for doctor's visits, which Australian Medical Association president Brian Owler said would result in additional costs having to be passed on to patients.

"We will see less bulk-billing and there is the possibility of seeing a co-payment by stealth, as has been alluded to by some," he said.

The proposed GP co-payment plan, which would have added $5 to the cost of a consultation, was jettisoned by the Abbott government in March.

However, research published in the Medical Journal of Australia in March found that in 2017, GPs would have to introduce a $8.43 co-payment for non-concession consultations to offset the difference caused by the freeze.