Malcolm Turnbull insists a corporate tax cut is crucial to boosting the economy in the face of global uncertainty.
The prime minister headed to marginal seats in Brisbane on the first full day of campaigning ahead of the July 2 election, as two new polls had the two major parties level-pegging.
The polls also showed a high proportion of voters gave the thumbs down to the budget - the centrepiece of which was a 10-year plan to lower the company tax rate to 25 per cent.
Labor says the $48.2 billion hit to revenue is unaffordable at a time when extra funding is needed for schools and hospitals.
But Mr Turnbull told reporters it would drive investment and jobs.
"It is very clear that as you reduce business taxes, you will get more investment and more employment and the Australian Treasury estimated last year for every dollar of company tax cut there was $4 of additional value created in the economy," he said.
The prime minister said business confidence would determine Australia's future.
Labor frontbencher Penny Wong said the coalition had overseen much "economic meandering" since 2013 and differed from Labor in its views about the future.
"The government is saying we want to give a big tax cut to big business and put the budget in a frail position," Senator Wong told ABC radio.
"Labor says they want to invest in people, in schools, in the future."
Finance Minister Mathias Cormann said the budget would have been in a better position had Labor not mismanaged it while in government and if the global economy had not weakened.
However, Senator Wong said Labor had successfully steered Australia through the global financial crisis.
Labor leader Bill Shorten is heading to Cairns on the first full day of his campaign.
Nationals leader Barnaby Joyce, campaigning in Tamworth, said he was hopeful the election would not be about personalities but "capabilities".
However, he warned the eight weeks would be gruelling.
"I'm looking forward to this election. It is going to absolutely knock the stuffing out of all of us, it is going to infuriate, bore, send people crazy," he said.
"What a wonderful thing democracy is."
The two houses of parliament were formally dissolved at a brief ceremony in Canberra on Monday morning.
Watch: PM officially calls first double dissolution election in almost 30 years
