The Coalition's promised savings from scrapping the National Broadband Network were $900 million out over four years, a Treasury analysis claimed.
Independent MP Rob Oakeshott posted on his website overnight the costing analyses of Labor and the Coalition's election promises that were prepared by Treasury.
They were handed to Oakeshott and the other independents by Treasury head Ken Henry in meetings that wrapped up last night.
Members of the Coalition put costing variances down to "differences in opinion with Treasury" in various interviews with the press today.
The Coalition had previously said that scrapping the NBN would save $2.44 billion over the next four years because the Government wouldn't be paying interest on borrowings to fund the network.
But the Treasury analysis claimed there needed to be a "reduction of $900 million over four years to public debt interest savings from reversing the ALP's policy to build the NBN" in the Coalition's costing projections.
The costing difference was reportedly due to the interest rate used in the respective calculations, Coalition finance spokesman Andrew Robb told a press conference in Canberra today.
The Coalition used a 5.5 percent rate; Treasury used 4.9 percent, Robb said.
That was supported by an official Coalition statement: "Several of the differences in the Coalition's and Departments' costings reflect different models and data," it said.
Coalition treasury spokesman Joe Hockey told ABC Radio's AM program today that the Coalition had a "difference of opinion with Treasury over nine or ten different policy" costings.
Hockey said the Coalition was "entitled to have a difference of opinion" but said it "emphatically" stood by its polices and numbers.
"Where there is a difference of opinion, the Treasury - as it states in its letter to us - had facts and figures that we did not have available and the public didn't have available so we had to use best endeavours to get our numbers," Hockey said.
"We stand by our numbers".
Hockey said the Coalition had attempted to explain the costing differences with Oakeshott and Queensland independent Bob Katter. Other independents had not been contactable, he said.