The minority government is expected to see carbon laws approved by parliament’s lower house on Wednesday, after a decade of debate and two previous defeats by lawmakers, then go through the upper house with the backing of Green allies.

Gillard hopes the success of the laws, which have already claimed the jobs of one prime minister and two opposition leaders, will bolster her support in the polls, although other plans which worry voters are still to pass.

“This was historic legislation,” Gillard told a closed meeting of Labor government lawmakers as parliament resumed. “Once in place, this will be a reform that gathers support,” she said.

The laws will force around 500 big polluting companies to pay for carbon emissions via a A$23 ($23) per ton carbon tax from July 2012, ahead of emissions trading from mid-2015.

Earlier plans to price carbon emissions were rejected in 2009.

But the Australian Industry Group, which represents manufacturers, said the package should be amended given global economic instability and pressures already facing manufacturers, including a high local dollar at parity with the US dollar.

Those concerns were echoed by the Business Council of Australia, which represents the top 100 companies, which called for safeguards to ensure climate action is only taken in tandem with other nations, warning the legislation was “neither workable nor responsible” without them.

A closely-watched Newspoll in The Australian newspaper on Tuesday said support for Gillard’s government had bounced back from record lows, but the conservative opposition still held a commanding 57-43 percent lead two years from new elections.

Gillard, in the top job for barely a year, has been under siege from the opposition over her plans for new taxes and for dealing with asylum seekers, and is now fending off media speculation about an eventual leadership challenge.

Some political analysts have given Gillard until Christmas to engineer a turnaround or be dumped, although a little-known Labor backbencher threatened on Tuesday to resign and erase the government’s one-seat majority were Gillard ousted.

Gillard’s minority government relies upon support from one Green three independents in the lower house.

Another vital vote was expected on Thursday. This covers changes to migration laws needed to clear an asylum seeker swap deal reached with Malaysia, but rejected by Australia’s High Court.

The Greens oppose the migration changes, and Gillard’s Labor has been desperately courting two conservative-leaning independents in a bid to avert the first lower house vote defeat for a government in 80 years.

It would be a blow for Gillard’s authority likely to fuel more talk of leadership challenges, but defeat of the migration changes would not bring down the government.

Less inflammatory but still contentious for Gillard, the upper house Senate on Wednesday was likely to pass world-first laws forcing tobacco firms such as Philip Morris , Imperial Tobacco and British American Tobacco to adopt plain olive-green packaging, a move likely to trigger a slew of court challenges.