Opposition Leader Bill Shorten says voters won't be bought off by a few dollars in tax cuts in Tuesday's budget.
Finance Minister Mathias Cormann has confirmed the budget will aim to tackle bracket creep, but has declined to go into specifics.
It is estimated that 300,000 middle income earners will be forced into the second highest tax bracket as wage inflation lifts their salaries above $80,000, otherwise known as bracket creep.
"We have been committed to doing as much as we can sensibly afford to ensure the average wage earner doesn't move into the ... second highest tax bracket," Senator Cormann told Sky News on Sunday.
But Mr Shorten said the government may be patting itself on the back for offering modest tax cuts, but Australians won't be falling for that tactic.
"For the last three years, every day, the Liberal government has been pick-pocketing voters and now at the very last minute they are offering a few dollars in hope that all will be forgiven," Mr Shorten told reporters in Melbourne.
Shadow treasurer Chris Bowen said the proposal that would see these changes from July 1 and the day before the expected federal election was "cynical", but did not rule out supporting it.
"The government seems to think that a small fistful of dollars might help the Australian people forget three years of chaos and attacks on their cost of living," he told ABC TV.
