Saul sounds skeptical

Coalition has $30b gap in promises: leading economist Saul Eslake

He predicts that the Coalition will ultimately adopt all of Labor's proposed budget savings measures, except for ending the tax break for cars bought through salary sacrifice.

Even so, Mr Eslake estimates, the Coalition has so far committed to $28.4 billion of tax cuts and $14.8 billion on new spending in the next four years, a total of $43.25 billion. But he estimates the nine savings measures the Coalition has announced so far would save only $13.44 billion over the same period.

"By our reckoning, over the remainder of the election campaign, the Coalition needs to announce additional savings measures totally in the vicinity of $30 billion over the four years to 2016-17 in order to be able credibly to claim that it would produce better bottom line outcomes than those projected (by Treasury and the Department of Finance), he said."

"That is a substantial sum, although it is considerably less than the $70 billion 'black hole' suggested by the government."