The Morrison government has pinned its re-election hopes on a $302 billion package of tax cuts to be rolled out over the next decade, unveiled in a budget that forecasts a surplus for the first time in 12 years and proposes paying off net debt by the end of next decade.

The budget, handed down just days before Prime Minister Scott Morrison calls an election for mid-May, also squirrels away $3.2 billion for the election campaign under the heading "decisions taken but not yet announced', matches Labor's tax cut pledge for 10 million people on low and middle incomes, and seeks to neutralise other key strengths of the Opposition