The coalition must find at least $16 billion in new spending cuts or back tax increases to stop the Budget going further into the red.
Although the Opposition has already identified $17 billion in savings - including cutting 12,000 public servants and delaying an increase in the superannuation guarantee - new figures from the departments of Treasury and Finance show the coalition needs to cut even deeper to prevent bigger Budget deficits.
The departments yesterday released their independently compiled Pre-election Economic and Fiscal Outlook which effectively mirrored the Government's own economic statement released a fortnight ago.
Treasury and Finance forecast the same Budget deficit for this year, at $30.1 billion, the next at $24 billion and in 2015-16, $4.7 billion.
The only change was an upward revision to the expected surplus in 2016-17, which was pushed up almost $200 million to $4.2 billion.
The biggest changes from the economic statement were a $400 million increase in the expected revenue from the mining tax and a $230 million lift in carbon tax revenues.
Both departments stuck with the same economic forecasts released by the Government, which include the economy growing 2.5 per cent this financial year with unemployment tipped to reach 6.25 per cent.
But the figures identified the size of the Opposition's challenge to improve the Budget bottom line.
Tony Abbott has pledged to keep the tax cuts and pension increases introduced by the Government to offset the impact of the carbon tax - a cost to the Budget of $12 billion.
Another $5 billion is needed to cover the cost of the coalition's pledge to cut the company tax rate by 1.5 percentage points.
However, the Opposition Leader has also promised to axe the mining tax, which the coalition maintains will fail to deliver any meaningful revenue to Federal coffers.