The Department of Human Services, which owns Medicare data, last week refused a freedom-of-information request from the Australian Healthcare and Hospitals Association for data on the number of people who are bulk-billed, on the grounds the information does not exist.

The refusal came after Health Department officials told a Senate estimates hearing last week it had not modelled the impact of the $7 charge on hospital emergency departments and follows National Commission of Audit chairman Tony Shepherd conflating visits to the doctor with Medicare items.

In a letter refusing the association's information request, the Department of Human Services said while it could be possible for it to produce such data, this would require computer programming, which would constitute ''a substantial and unreasonable diversion of the department's resources''.

Medicare publishes data on the numbers of services that are bulk-billed. Last financial year, Medicare was billed for about 116 million GP visits, about 81 per cent of which were bulk-billed. But the proportion of people who received bulk-billed services is less, because some bulk-billed patients use more services than the average patient.

Health Minister Peter Dutton has said since the budget that 70 per cent of non-concessional patients are bulk-billed. When asked for the source of this claim, his department pointed to internal calculations that showed 70 per cent of Medicare services delivered to non-concessional patients were bulk-billed, but did not explain what proportion of non-concessional patients were bulk-billed.

Australian Healthcare and Hospitals Association chief executive Alison Verhoeven said: ''The co-payment policy is rapidly becoming an evidence-free zone, with the Commission of Audit claims about GP attendance rates being disproved, no apparent efforts made to model the potential impact and no baseline data available to evaluate its effect over time.''