The federal budget's forecast bottom line has gone backwards by at least $80 billion since the Coalition came to office, challenging the Prime Minister's promise that a tough budget is not needed this year because the nation's finances are under control.

The estimate by The Australian Financial Review covers the period to the end of last year. It therefore does not include around two-thirds of total announced cuts and tax increases of $28 billion that have have been abandoned by the Coalition, rejected by the Senate or are likely to be dumped.

Prime Minister Tony Abbott this week dumped the last remnants of tough rhetoric about budget savings, and instead promised voters they did not have to be alarmed about this year's "dull" budget "because we have got the budget situation from out of control to manageable".

On Thursday, the government pushed back at suggestions it had dropped the ball on budget repair, saying "there was much more to be done".

The budget papers show that, even before the government dumped its plan for a $7 Medicare charge and university spending cuts, the cumulative budget deficits for 2014-15 to 2017-18 have blown out from a forecast of $24.5 billion to $103.9 billion