Former treasurer Peter Costello and the head of the Abbott government's financial system inquiry, David Murray, have both delivered a strong rebuke to suggestions first home buyers could be given access to their superannuation early.
Mr Murray's comments come after the federal government said it was considering allowing people to tap their super to help buy a home.
"To divert money into housing at any stage during the build-up in superannuation savings is not consistent with having a good retirement income system," he told Sky News on Tuesday.
"It should be there for retirement."
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The former boss of the Commonwealth Bank and the Future Fund said if money was taken out of super for housing during a person's working life, some money from that housing should be put back into a retirement income when they retire.
"I don't think that would be a very attractive solution, but it would at least level it up," he said.
Mr Costello reiterated Mr Murray's concerns saying super has two purposes - increasing retirement savings and reducing pension costs - and the government should not give multiple objectives, "none of which it will actually do very well".
Prime Minister Tony Abbott has welcomed debate on the idea, but Labor, economists and former PM Paul Keating have all warned it will only push up house prices and erode retirement savings.
Mr Costello says the Howard government looked at opening up superannuation to home buyers in the 1990s, but decided it should instead be preserved for retirement savings.
It was "fair enough" for the Coalition to again have a look it, he said.
"But I think they will come to the same conclusion as we did: that if you wanted to top up people's retirement, if you wanted to save the government money ... then you probably won't allow people to draw down on it for housing," he told ABC Television.
Mr Costello's comments come as Labor leader Bill Shorten prepares to make a key speech on superannuation in Melbourne.
In an address at Monash University, Mr Shorten will argue Australia's savings pool will be almost $1 trillion worse off within four decades because of Abbott government superannuation decisions.
He will say the government is being short-sighted by freezing the superannuation guarantee and scrapping the low income superannuation contribution.
An average income earner, aged 25, will retire with $100,000 less in savings, according to modelling to be released by Labor.
"The Liberals' attack on Australia's world-class compulsory superannuation scheme will undermine retirement savings by nearly one trillion dollars and put greater pressure on the age pension," Mr Shorten will say on Wednesday.