Labor has joined the coalition in ruling out deals with minor parties and independents to form a minority government if the federal election result is tied.
Prime Minister Kevin Rudd's decision came as Opposition Leader Tony Abbott directed the Liberal Party to put the Australian Greens last on all lower house how-to-vote cards.
Labor's ambition is to win majority government, after three years of governing in minority with crossbench support.
"That is the best thing for the nation," Mr Rudd told reporters in Cairns on Wednesday.
"We will not be entering into any coalition agreements. We won't be having any negotiated agreements. We won't have any deals with any independents or any minor party."
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Mr Abbott, who earlier in the campaign made the same pledge, said minority government had been an "experiment that failed".
He challenged Mr Rudd to "show some leadership" and also put the Greens last.
Mr Rudd said preference decisions were a matter for the ALP organisation.
Deputy Prime Minister Anthony Albanese said Labor was making preference decisions on a seat-by-seat basis ahead of the September 7 poll.
Greens leader Christine Milne said the major parties felt threatened by her party's success.
"They don't have a different philosophical view. In fact, both Kevin Rudd and Tony Abbott could be sitting in the same car, looking in the same rear-vision mirror," she said.
Senator Milne argued the Liberals couldn't govern alone after the election anyway because they were in coalition with the Nationals.
The two major parties are finalising preference deals.
The clash came as the 54 parties contesting the election, as well as independent candidates, were finalising their preference deals ahead of the close of election nominations on Thursday.
The Senate's group voting ticket, which determines preference flows when voters cast an "above the line" ballot, will be finalised over the weekend.
High-profile Labor candidate Peter Beattie on Wednesday made a last-minute pitch to Katter's Australian Party (KAP) for preferences.
Labor and the coalition are courting Bob Katter's team for preferences, especially in Queensland where their vote is expected to be strongest.
Mr Katter flew to Melbourne earlier this week for talks on the issue with Liberal federal director Brian Loughnane.
Mr Rudd is understood to have spoken with Mr Katter before the campaign began.
"I don't see any difficulty, assuming I get elected - and that is up to the people of Forde - working with Katter," Mr Beattie said.
"He shares with Kevin Rudd and I a passion for Queensland and that passion will actually make sure that Queensland is given the sort of recognition it should ... in the national capital."
Mr Katter, who is likely to hold the seat of Kennedy, told reporters in Brisbane he's not leaning towards any party when it comes to preference swaps.
He said there was a lot of "wheeling and dealing" to be done before any preferences are decided.
KAP is expected to poll strongest in the seats of Herbert and Dawson and could also have influence in Capricornia, Flynn and Leichhardt.
There is also the prospect of picking up a Senate spot at the expense of Labor.
