The age for superannuation needs to be raised and people should have to live longer in the country to be eligible, the Retirement Commissioner says.
Currently anyone who has lived in New Zealand for more than a decade and is over 65 is entitled to the national super scheme.
But Retirement Commissioner Diane Maxwell told TV3's The Nation the system is unsustainable because of increasing lifespans, and the age needs to be gradually raised from 65 to 67 over the next decade.
"The number of 65-plus will double in the next 25 years. The cost of super will triple in the next 20 years."
She said on average OECD countries required people to be residents for at least 26 years to be eligible for super schemes, and New Zealand needed to look at shifting its criterion towards the 25-year mark.
She said the Government would then need to use the $1.6 billion in savings from those changes to help those in jobs that could not be done into old age.
"We have two groups here: one that could frankly work to 70 without a problem, but for others 65 isn't the issue. If they have an issue at 65 they would have had an issue at 55," she said.
"Is it a career change? Is it retraining? What do they need?"
But Commerce Minister Paul Goldsmith said the cost of super would only go up from 5 per cent of GDP to 7 per cent in the next three decades and there was no need for cuts.
"If you keep good, sound control of the finances, there's no reason to think that New Zealanders can't afford to look after older people."