SYDNEY: Three former Australian prime ministers have joined the country`s bitter election campaign, giving a boost Friday to both sides of politics two weeks before neck-and-neck polls.

Former prime minister John Howard branded incumbent leader Julia Gillard`s tenure a "total failure", while another ex-Liberal Party leader Malcolm Fraser on Friday turned on his former party saying it was not ready to rule.

The extraordinary interventions by the former PMs came a day after Kevin Rudd, who was ousted as prime minister by Gillard in a Labor Party coup six weeks ago, promised to campaign for his political assassin in a show of unity.

Conservative Howard, toppled by Rudd`s Labor Party in a 2007 election after more than 11 years in power, said Gillard had been a "total failure" on the issue of asylum seekers, climate change and a controversial mining tax.

"And in my view an even bigger failure than her predecessor (Kevin Rudd)," he told Liberal party supporters in Sydney late Thursday after being rolled out to counteract Rudd`s reappearance.

"This government at its core is an incompetent government," he said.

But fellow Liberal Fraser, prime minister from 1975 to 1983, turned on his old party, now led by conservative Tony Abbott, a Howard protege.

`No," he said categorically when asked in a radio interview if the opposition was ready to return to government, refusing to comment further.

The flurry of ex-prime ministerial apparitions came after Rudd made a political come-back Thursday supporting Gillard`s government and launching a blistering attack on Abbott, accusing him of "economic vandalism".

Gillard and Abbott were Friday wooing crucial marginal voters ahead of the August 21 election that opinion polls show is shaping up as a cliffhanger.

Australia`s first woman leader called the vote to win her own mandate after ousting Rudd, who oversaw Australia`s emergence from the global financial crisis in better shape than other advanced economies.

Key issues in the lacklustre campaign include economic management, tackling the flow of boatpeople from Asia, global warming and health care reforms.

However fundamental policy differences between the candidates are minimal and both are committed to returning the budget to surplus, so they have focused on minute tweaks of their platforms and on attacking each other`s records.

BDST: 9:45 HRS, August 05, 2010