Those who can do heavy lifting will:Hockey

Treasurer Joe Hockey says most of the heavy lifting in the May budget is going to be done by those who "have the capacity", after flagging major spending cuts.

Mr Hockey on Wednesday night unveiled details from the soon-to-be-released commission of audit, which shows government spending has almost tripled in the past 40 years.

Over the medium term, the commission expects the 15 largest and fastest growing government programs will be welfare, health, education and defence - and in most cases it says these will grow considerably faster than the economy.

Mr Hockey has flagged cuts across the board when the budget is handed down on May 13 and hasn't ruled out tough means testing for support payments and co-payments for government services.

There could also be a rise in the pension age to 70, from 67.

Mr Hockey said the age pension was only ever meant to be a safety net.

"The heaviest lifting is going to be done in the budget by those that have the capacity to do the heavy lifting," he told Macquarie Radio.