CANBERRA - In what could be a defining moment of the campaign for the August 21 election, former Labor Prime Minister Kevin Rudd yesterday moved to pull the weight of his dismissal from the Government's back and throw the attack onto the Opposition.

Rudd confirmed his loyalty to successor Julia Gillard - whom he will meet tomorrow for the first time since the aftermath of the leadership coup - and, given clearance by his surgeon after his gall bladder operation, will join the national campaign on Sunday.

Rudd's brief media appearance in Brisbane, also the first since his ousting, was intended to end the intense speculation that has thrown the Government's campaign off the rails for the past two weeks and allowed Opposition leader Tony Abbott a dream run.

Labor has been consumed by the fallout of the coup and a series of damaging leaks from high within the Government, with Rudd a major suspect.

The impact has been shown clearly in opinion polls, which, since Gillard's early ascendancy, have charted a sharp reversal, placing the Coalition within reach of victory and dramatically narrowing Gillard's lead as preferred prime minister.

Yesterday a new Morgan poll said the two parties were now 50-50 in the two-party preferred vote that determines Australian elections, with the Coalition gaining a strong 45 per cent to 38 per cent lead in primary votes.

The poll also showed a large fall in Gillard's support among women: the two-party female vote for the Opposition has now nudged ahead of support for Labor, running at 50.5 per cent to 49.5 per cent.

The latest Reuters poll trend averaging the results of the three major polls, also released yesterday, found support for Labor had slipped by 2.5 per cent to 51.5 per cent since the campaign started three weeks ago.

Reuters said if it was repeated uniformly across the nation on polling day, Gillard would scrape back into office with a reduced majority, and could even be forced to deal with independents to retain power.

Australia's last hung federal Parliament was in 1940.

Rudd said he had decided to speak out because there were bigger things at stake than his own future, and to help bring the "necessary focus" to the campaign about what Abbott would do to the country if elected prime minister.

In an earlier interview on ABC radio, Rudd had denied leaking confidential Cabinet information in revenge for his ousting: "Something my mum taught me years ago is life's just too short to carry around a great bucketload of anger and resentment and ... all that sort of stuff."

If Rudd had not appeared publicly and agreed to high-profile electioneering, Gillard's campaign would have continued to be undermined, and would have presented a real dilemma for Labor's campaign launch in aweek.

Whether he appeared or not, Rudd would have obscured the message.

His re-emergence yesterday, declaring that he was "not a quitter" and announcing plans for campaigning in Queensland and New South Wales, will have two immediate benefits.

It will cloud Abbott's announcement yesterday of his intention to take full funding control of the nation's hospitals, and will distract from the Coalition's official campaign launch on Sunday.

Gillard has welcomed Rudd's appearance, which shifted rapidly from his own position to a concerted attack on Abbott, who he said would tear down all Labor had done in health and education, axe the new national broadband network in an act of "national vandalism", and endanger an economy still at risk from further global turmoil.