The figures are a major blow to Liberal leader Tony Abbott's bid to become prime minister of Australia's first minority government since World War II after August 21 elections failed to deliver any party a majority.
The Liberal Party represents the conservative spectrum in Australian politics, despite its name, and vies for power against the Labor Party.
The three kingmaker nonaligned legislators had requested briefings from Treasury and Finance Ministry bureaucrats on confidential estimates of competing election pledges.
They said the questions of which party had the best economic blueprint, and which might have misled voters were key factors in deciding whether to back a Liberal Party-led coalition or Labor Party government.
The trio released Treasury documents late Wednesday that contradicted Abbott's claim that Australia's bottom line would be $A$11.5 billion ($10.5 billion) better under his conservative coalition.
Treasury found that the improvement could be as little as $A900 million.
Independent Tony Windsor said today he would ask coalition lawmakers to explain the discrepancy before commenting on how it would effect the choice he will make as early as tomorrow.
"It's not a good thing for the coalition," Windsor told Australian Broadcasting Corp. radio. "They're enormous numbers."
The coalition released a statement saying it stood by its projected savings and saying that in government, the coalition could change the way Treasury made its calculations.
Prime Minister Julia Gillard had urged the independents to make public the costings of the coalition and her own Labor Party which has governed for the past three years.
Treasury found that Labor had understated the improvement to the budget position under Labor's policies by AU$62 million ($56 million).
Deputy Labor leader Wayne Swan told ABC the coalition costings were "either deliberate dishonesty, incompetence or both."
Greens party lawmaker Adam Bandt on Wednesday became the first of five lawmakers from outside the major parties to announce which side he will back.
His support gives the center-left Labor Party control of 73 seats in the 150-seat House of Representatives, the same as the conservative coalition.
Labor remains in charge of the caretaker government until Gillard or Abbott can strike a deal with independents to command 76 seats. If neither leader can command a majority, new elections will be called.
