Opposition treasury spokesman Joe Hockey has suggested Tony Abbott is more of a straight talker than Kevin Rudd because he broke a promise before, rather than after, an election.
The opposition leader was grilled on Monday night about his broken promise earlier this year not to propose any new taxes.
"Sometimes in the heat of discussion you go a little bit further than you would if it was an absolutely calm, considered, prepared, scripted remark," Mr Abbott told ABC TV.
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"The statements that need to be taken absolutely as gospel truth are those carefully prepared, scripted remarks."
Mr Hockey says his leader's stance proves he's more honest than the prime minister.
"The thing about Tony Abbott is he's a straight talker," Mr Hockey told ABC TV.
"The thing about Kevin Rudd is he makes promises and then breaks them after the election. That's the difference."
Mr Hockey said the PM had broken promises on hospitals, private health insurance and climate change.
Mr Abbott was simply being upfront about the fact governments shouldn't make promises they couldn't afford.
"I only wish the (Rudd) government had learned that lesson," Mr Hockey said.
Mr Abbott pledged in February a coalition government wouldn't introduce new taxes. But a month later he announced a "modest and temporary levy" on big business to fund a paid parental leave scheme.
Finance Minister Lindsay Tanner says Mr Abbott has admitted the public can't trust anything he says in the heat of battle.
"For the first time in Australia's history we've got a political leader saying `Don't trust what I say get it in writing'," Mr Tanner told ABC TV.
"The trouble with that is there isn't anything in writing.
"There's nothing there to read. All we get from Mr Abbott is thought bubbles and these scare campaigns."
