Scott Morrison is expected to face more questions over the coalition's handling of the Murray-Darling Basin as the leaders return to the campaign trail after the Easter truce.
Labor is trying to flush out more details of an $80 million water purchase in 2017, the largest on record, amid growing calls for a royal commission into the river system.
Opposition Leader Bill Shorten is in north Queensland where he will pledge to tear up a controversial $444 million grant the Turnbull government handed to the Great Barrier Reef Foundation.
The government came under fire over the taxpayer-funded payment because the small organisation was given the lump sum without a competitive tender process.
Labor is also pledging more money for tourism, including matching the coalition's pledge to spend $100 million on upgrading regional airports.
Mr Morrison is returning to Victoria for the second time in a week, as the coalition looks to save crucial seats in the battleground state.
He has spent much of the campaign talking up the coalition's economic management credentials, linking the state of the budget to the ability to provide money for education and health.
But the prime minister's camp is remaining tight-lipped about its plans for Monday as it aims to avoid protesters or other awkward interruptions on the campaign trail.
The government has fended off questions about the $80 million water buyback, arguing there has already been a Senate inquiry into the matter and the government had provided documents regarding those transactions.
The Greens want Labor to back a royal commission into the purchase if Mr Shorten becomes prime minister after the May 18 election.
A campaign ceasefire was entered into by the leaders of the major parties on Easter Sunday and Good Friday, and are set for another truce on Anzac Day.
Australian Associated Press