Tony Abbott says the community expects politicians to stretch the truth "in the heat of verbal combat" but his scripted remarks can be taken as "the gospel truth".
The opposition leader was grilled on Monday night about his broken promise earlier this year not to propose any new taxes.
During a radio interview in February, Mr Abbott pledged a coalition government wouldn't introduce new taxes.
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But a month later he announced a "modest and temporary levy" on big business to fund a paid parental leave scheme.
On Monday night he tried to explain the backflip.
"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.
"The statements that need to be taken absolutely as gospel truth are those carefully prepared, scripted remarks."
The opposition leader said people could tell when to put "absolute weight on what's being said and when it's just the give and take of standard conversation".
The truth could be lost in the "heat of verbal combat", he suggested.
But Mr Abbott repeatedly denied he'd gone back on his word.
"It (proposing a new tax) wasn't absolutely consistent with what I said the month before," was as far as he'd go.
"There is a bit of inconsistency."
Monday's interview with the 7.30 Report's Kerry O'Brien was meant to be about the opposition leader's budget reply speech, delivered last Thursday.
Prime Minister Kevin Rudd was accused of losing it during his post-budget interview on the program last Wednesday.
A visibly angry Mr Rudd dismissed a suggestion he'd shown political cowardice on climate change by deferring his emissions trading scheme until at least 2013.
The PM said he sat up for three days and three nights to try and frame a global agreement at the Copenhagen climate conference late last year.
"Now, it might be easy for you to sit in 7.30 Report land and say that was easy to do," Mr Rudd told Mr O'Brien.
"Let me tell you, mate, it wasn't."
Mr Abbott said his promise not to bring back the coalition's Work Choices regime was the real deal.
"That is a very considered position," the opposition leader said.
Earlier, he dismissed an accounting expert's claim that the coalition's plan to save $4 billion over four years through a public service jobs freeze was unrealistic.
Sydney University accounting professor Robert Walker says Mr Abbott's number-crunching overstates savings by $1 billion.
The opposition leader either overestimated wages or assumed public servants all quit at the start of a financial year, he said.
But Mr Abbott said his costings were "conservative".
"If there really was a big problem with our costings the government would have been out of the blocks on Friday."
The opposition leader also stood by his budget reply pledge that a coalition government would roll back Labor's proposed resources rent tax.
The Rudd government's new mining tax was entirely different to his paid parental scheme levy, he said.
"This $9 billion a year hit on our most successful industry is fundamental economic vandalism.
"A decent paid parental leave scheme is not only long overdue, not only socially visionary but is a fair dinkum productivity measure.
"It will help the economy."
Deputy Prime Minister Julia Gillard wasted little time in trying to capitalise on Mr Abbott's comments.
"Every Australian should be concerned whether they can trust a single word Tony Abbott says," Ms Gillard said in a statement.
"The public will simply never know whether it is 'gospel truth' Tony Abbott speaking or whether they are hearing phoney Tony."
