The Labour Party leader is calling for a cross-party discussion on the need to raise the age of eligibility for New Zealand Superannuation.
In a pre-Budget speech in Christchurch on Monday, David Shearer says his party will face up to the looming cost of superannuation.
Mr Shearer says Labour will stick to its pre-election policy of raising the pension age.
However, he says the party raised the issue too late last year and there needs to be much wider discussion to get consensus on the matter
Mr Shearer believes the existing system is unaffordable.
At present, there are 5.6 working people for each retired person, but in 30 years that will more than halve to 2.5.
David Shearer says unless something changes, young people will have to give up their education and health opportunities to pay for older people's retirement.
The Budget will be delivered on Thursday afternoon.