Shadow Treasurer Joe Hockey insists he doesn't believe in austerity-style cuts but admits the coalition is looking at "all other areas" outside of defence, health and medical research for savings.
Mr Hockey made the comments on Monday in an hour-long debate with Treasurer Chris Bowen.
"If you don't have any sense of prudence, then you are not going to get the budget back into surplus," he told ABC television's Q&A program.
"I don't believe in austerity, as it's defined, but I believe in being respectful and careful of other people's money."
Mr Hockey was asked what areas of spending the coalition was not prepared to cut.
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"We've got to build defence spending over time and we've quarantined that, and health and medical research is incredibly important, and we've guaranteed that," he said.
But "all other areas" would be looked at for possible cuts, Mr Hockey added.
"There will be restructuring, of course there will be - there has to be," he said.
Mr Hockey reiterated that the coalition had committed to matching the federal government's spending on its Better Schools Plan for the next four years.
Mr Bowen said returning to surplus was an important goal "but shouldn't be your first obligation".
"Your first priority should be to keep the economy strong, add jobs and growth," he said.
Achieving a surplus "tomorrow or next year" could be done, but it would mean cutting services or increasing taxes.
"It can be done but it would be the wrong thing for the economy," the treasurer said.
