Australian Prime Minister Julia Gillard spent her third anniversary in office resisting pressure from colleagues to open her job to a ballot less than three months before national elections.

A new opinion poll suggests her ruling centre-left Labour Party is headed for a devastating defeat at the elections set for Sept 14.

Pressure has mounted as Gillard has failed to lift the dismal polling, and the cloud over her leadership of the party is distracting the public from her policy messages.

Gillard became Australia’s first female prime minister when she ousted Kevin Rudd on July 24, 2010, in an internal party coup. Successive polls suggest Labour would be more popular with voters if Rudd instead of Gillard was party leader, so many in the government want Rudd back.

Gillard opened herself to a ballot of Labour lawmakers in March to prove most of them supported her. Rudd refused to challenge then because he couldn’t be guaranteed a decisive victory. He explained he did not want to lead a divided party, and the ballot fizzled without him.

She said today she would neither quit nor put her leadership to another vote. “This issue was settled in March so that’s the end of it,” Gillard told reporters.

Pressure mounted for a ballot this week because it’s the last time government lawmakers will be together at Parliament House before the election which the conservative coalition lead by Tony Abbott appears destined to win in a landslide.

Senior government minister and Gillard ally Greg Combet said the leadership speculation was risking further damage to the party.

“I think Kevin Rudd does need to decide what he is going to do here,” Combet told Australian Broadcasting Corp.

Rudd has publicly ruled out a challenge, although many suspect he could change his mind.

Labour lawmaker Stephen Jones said the party leadership had to be settled and “probably the best way to resolve it would be a ballot.”

A poll by Sydney-based market researcher Newspoll published in The Australian newspaper on Monday found Labour lagged well behind the coalition. Labour had 43 per cent of voter support and the coalition had 57 per cent.

The poll was based on a random nationwide telephone survey of 1,140 voters at the weekend. It has a 3 percentage point margin of error.

The influential The Age newspaper took the unusual step on Saturday of calling for Gillard to stand aside as leader in a front page editorial.

“The Age’s overriding concern is that, under Ms. Gillard’s leadership, the Labour Party’s message about its future policies and vision for Australia is not getting through to the electorate,” the editorial said.