Health Minister Peter Dutton insists the Medicare co-payment is a "sensible change" to the health system which will pass parliament.
But he won't get any support from Labor, after Opposition Leader Bill Shorten told a 200-strong rally outside Old Parliament House in Canberra that the plan would be fought "to the death".
The government is struggling to find support on the Senate crossbench for the $7 co-payment which is to go into a new medical research fund.
The Palmer United Party has joined Labor in condemning the idea.
At least three government MPs have also publicly voiced concern about the budget measure, arguing for exemptions for pensioners and the elderly.
Mr Dutton told reporters in Canberra on Wednesday the government was confident the measure would be passed once senators understood the need to make the Medicare system sustainable.
"We are making sensible changes and that's why I believe they will be supported through the Senate," Mr Dutton said.
"I believe we can work constructively with those people that want a sustainable Medicare."
Mr Dutton said there was an equal amount of trepidation about the government's perceived "doomed" financial advice changes but they still passed after upper house negotiations.
He would not be drawn on new polling data showing 40 per cent of Australians over 50 considered a co-payment a vote-changer at the next election, instead welcoming the part showing most were favour of making health contributions.
Labor says the government will eventually be forced to back down on the co-payment because there can be no middle ground on a new tax on the sick.
"They should put that in the bad idea waste bin and start again," Opposition Leader Bill Shorten told a Canberra rally marking the 40th anniversary of Medicare.
The government does not have a specific date on introducing the laws, which it wants to start from July 2015.
Mr Dutton said he was not considering means other than legislation.
Share
