Opposition Leader Tony Abbott says Treasury costings showing his election promises were off by between $7 billion and $11 billion are just a matter of a ``difference of opinion''.
Mr Abbott refused to issue his policies for costing by Treasury and Finance during the election campaign, blaming the leak of details of the cost of his proposed paid parental leave scheme.
However, he agreed to requests from the three Independent MPs who will decide who forms government, and let the public service look over his numbers after the election resulted in a hung parliament.
Key independent Tony Windsor has expressed concern about what he described as a black hole.
''We probably understand now why he wasn't interested in releasing the numbers,'' he said.
''One of those things that we have to establish is trust in what they're actually saying.''
Fellow independent Rob Oakeshott has also expressed concern this morning.
The Treasury costings were issued late last night and showed the Coalition's policies would boost the budget bottom line by between $900 million and $4.5 billion, not the $11.5 billion claimed during the campaign.
Treasury also found Labor's promises would improve the bottom line by a slightly better than expected $106 million, not the about $44 million claimed during the campaign.
Mr Abbott said the bottom line from the costings was that the Coalition would still deliver larger surpluses than Labor and is standing by his figures. He said he would deliver $11 billion more in surpluses than Labor.
''Certainly there is absolutely nothing in any of the toing and froing over the last 12 hours or so that compromises our ability to continue to engage in good faith discussions with the independents about forming a stable and competent government for the next three years,'' he said.
He was very happy with the way Treasury and Finance had dealt with his costings.
Opposition treasury spokesman Joe Hockey said about $5 billion of the shortfall - which was not a black hole because it was coming from surpluses, not from deficits - was a matter of a difference of opinion with Treasury.
''We emphatically stand behind our numbers,'' he said.
Finance spokesman Andrew Robb said those differences reflected different data and models, for example, they had used different interest rates to calculate savings.
Mr Abbott said an ''arcane debate about costings'' and what interest rate was used in calculations was not the most important issue in the negotiations with the independents.
The parties' competing economic records were also fundamental to the discussions, and he said Labor's involved waste and mismanagement and debt and deficit, compared with the Coalition's history of responsible economic management and paying off debt.
However, Labor has pointed to strong economic data issued yesterday showing good growth while the rest of the developed world is still recovering from the global financial crisis.
Treasurer Wayne Swan said the Coalition had opposed the stimulus measures that protected the economy, and Treasury's revelations about their costings showed ''just how bad their economic judgment is and how unqualified they are to run the economy''. He accused them of being either deliberately dishonest or incompetent or both.
''They set out to deliberately deceive the Australian people and the verdict is in from the Treasury,'' he told the ABC.
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