Nearly 80,000 older Australians are expected to dump their private health cover by the end of the decade as a result of the federal government's controversial proposed changes.
The latest estimate is nearly double the 44,000 figure repeatedly cited by the federal government in defence of the policy.
The proposal would wind back the rebate Australians aged 65 and over receive on their private health cover, banking about $3 billion to spend elsewhere in the aged care system.
However health department analysis released under Freedom of Information (FOI) laws reveal that while 44,000 Australians are expected to drop their cover in 2028-29, that is forecast to rise to 78,000 just one year later.
The Coalition said Health Minister Mark Butler had consistently used the smaller figure to defend the policy.
Anne Ruston says older Australians cannot afford to live without private health insurance. (ABC News: David Sciasci)
"Either he didn't read his own briefs, or he's been deliberately misleading older Australians,"
Shadow Health Minister Anne Ruston said.
The health department said the estimate of 44,000 represented the "initial effect of the policy at a point in time" and noted the estimates were subject to uncertainty, as they were based on historical data and responses which might not reflect future behaviour under new policy settings.
Calls for Greens to block legislation
The proposal has come under increasing scrutiny, with the states and territories, aged care advocates and the private health insurance industry all raising concerns about whether the move would heap pressure on the public health system and impact vulnerable older Australians.
The federal government is counting on the $3 billion in expected savings from the changes, having already promised to funnel the money into other major aged care commitments.
However with the Coalition already vowing to block the legislation in the Senate, the federal government must get the Greens on board for the bill to pass.
The minor party has been playing hard ball, declaring last week it would not support the legislation in its current form.
Last month, the ABC revealed about $1.6 billion of the forecast savings would be clawed back from pensioners, according to Parliamentary Budget Office analysis.
Health department figures also revealed that of the more than 3.2 million older Australians affected by the changes, about two million live on less than $37,000 a year.
The Greens are now canvassing different options to amend the legislation, such as exempting pensioners from the changes.
Independent MP Monique Ryan called on the Greens to thwart the bill.
"This is a measure which affects pensioners more than any other group, and particularly affects low-income pensioners, so the Greens should come to the table and they should block this measure," Dr Ryan said.
"This is a government which is refusing to be transparent about a really important measure and Australians need to hold them to account."
Outside Parliament, health economists like former health department boss Stephen Duckett backed the policy, saying the impact on the public health system would be trivial.
Public policy think tank The Australia Institute also argued the money could be better spent on services that improve health and reduce hospital demand.
Mark Butler announced the changes to private health for older Australians in a pre-budget speech earlier this year. (ABC News: Callum Flinn)
A federal government spokesperson said the changes were about "making the private health insurance rebates fairer" and the overall number of people with private health insurance would continue to increase.
"The current additional rebate is simply not the best way to spend precious taxpayers' dollars on behalf of older Australians when we need to do so much heavy lifting in aged care," they said.
"Every dollar will be reinvested to deliver more aged care beds, more packages and better care for older Australians."