The Winnunga Nimmityjah Aboriginal Health Service has decided it will not charge the co-payment if it goes ahead, but the bold move could leave the organisation, which sees 130 patients a day, forced to absorb a yearly loss of $350,000.

There are also fears the move could see the service overwhelmed by demand and inundated with other needy patients unable to afford the co-payment, which is set to be introduced next year.

Chief executive Julie Tongs said the majority of the health service's clients would not be able to afford the co-payment.

"It's a big issue for the community and the whole country when you start to charge a co-payment for Medicare, which is a universal health system,'' Ms Tongs said. ''When you start winding it back, it's fraught with risk and there will be people who can't afford to access care.''

About 5500 people, including 4000 regular clients, use the Winnunga Nimmityjah Aboriginal Health Service every year. About 18 per cent of Winnunga's clients are non-Aboriginal.

Ms Tongs said demand for the service had nearly doubled in the past two months alone, with the organisation's client base surging from 80 people a day to 130.

"The risk for us, even to absorb the co-payment with what we've got now, is that it is going to tip other people over the edge that are accessing mainstream services and they would then come to Winnunga and that cost would then blow out," she said.

"I think what we will have to do is probably look at restructuring the service. The money that we are able to generate, Medicare income, goes back into primary healthcare so we fund doctors and other health professionals out of that funding. What that would mean is we would probably have to drop one or two doctors and that wouldn't be ideal either because of the number of clients."

A spokesman for Assistant Health Minister Fiona Nash said Ms Nash met with stakeholders including Winnunga last week and "will continue to engage with stakeholders about the measure and its implementation".

"The government will also invest $3.1 billion in indigenous-specific health programs over the next four years, an increase of more than $500 million over the previous four years,'' he said. ''Key areas of child and maternal health and chronic disease prevention and management will be expanded.''

Federal opposition health minister Catherine King said it was "inconceivable" that the government would try and force the co-payment on services such as Winnunga.

"It shows how out of touch the government really is that the Prime Minister doesn’t care or doesn’t understand that $7 is a lot of money for patients attending Winnunga and will be the difference between them seeing the doctor or not," she said.

ACT Chief Minister Katy Gallagher said it was probable that there would be changes to the co-payment when it is negotiated in the Senate, although the exact nature of the changes were unclear.

"If a clinic steps in and starts paying the co-payment, it will attract a whole range of clients to that service, so it will be a honey pot in the system, so there are some other issues, I think, that need to be thought through if exemptions are going to be given," she said.

She said the ACT government, which provides Winnunga with about $2 million a year, could not afford to step in and help the services with any losses that might be incurred by not charging the co-payment.

"We can't afford to go around the health system patching up the holes that have been created by the federal government," she said.

"We just can't afford it. We've got a big issue in our public hospitals now that I have to deal with, but I can't go around supporting primary care as well. There just isn't enough resources for that.

"We work in partnership with Winnunga and will continue to work with them to make sure we're doing everything we can to support them. I can't fill the gap for them and then every other general practice in Canberra. It's just not feasible."

Ms Tongs said Winnunga was also encouraging people to sign its petition against the co-payment and changes to the Pharmaceutical Benefits Scheme.

"I'm really shocked. I know the government has to do something if there is a budget black hole, but I don't think doing what they're doing, especially with Medicare, is the right policy, and especially doing it off the back of sick, poor people," she said.

"It's just not a fair policy whichever way you look at it."