Australian government unveils $2bn rail link pledge to woo key Sydney voters

• Australian prime minister Julia Gillard, centre, faces the cameras Picture: AFP/Getty

Australia's Labour government has unveiled its biggest election promise, a AU$2 billion (1.15bn) rail link in western Sydney, highlighting its struggle to win marginal urban seats to secure a second term on 21 August.

Prime minister Julia Gillard must win key marginal "mortgage belt" seats in Sydney and Melbourne, as well as marginal seats in the resource states of Queensland and Western Australia where there is strong opposition to a planned 30 per cent mining tax.

Ms Gillard, campaigning yesterday in Sydney, tried to focus on her economic credentials. But she had to fend off questions that have dogged her campaign in the wake of a June party coup which unseated predecessor Kevin Rudd.

"I made a judgment and I stand by it," Ms Gillard said, defending her part in the coup.

Labour continues to hold a narrow election-winning 51 per cent to 49 per cent lead over the conservative opposition, but a Newspoll in The Australian newspaper yesterday showed huge differences in support between states.

The Liberal-National opposition has opened a big lead in Western Australia, where Labour backing has been ravaged by the party's plan for a mining tax on iron ore and coal mines, and holds a clear lead in the other key resource state of Queensland.

Defeat for Labour would see its proposed tax on profits of mining companies scrapped by the opposition, along with plans to introduce carbon-trading and build a $43bn fast broadband network.

Conservative leader Tony Abbott needs to win only nine more seats to form a government with four independents MPs or 13 seats to take office outright.

Ms Gillard has come out fighting after a poor start, appearing confident this week before another live audience that had previously unsettled Mr Rudd, presaging the disastrous slide in his support that led to Ms Gillard's rise.

Mr Abbott, has, in contrast, been widely criticised over an interview in which he confessed to know little about his coalition's key policy for faster broadband, saying he was "no tech-head" in the vast continent where communications are a major issue.

While Ms Gillard has promised to abandon the campaign caution now choking voter interest by showing the "real Julia", the usually combative Mr Abbott has looked tentative.

"Tony Abbott has made an extraordinary personal journey from brash to meek without passing through humble," wrote veteran political journalist Malcolm Farr in the mass-selling Daily Telegraph newspaper.

In Labour's biggest single promise so far, Ms Gillard yesterday pledged AU$2.1bn to help build a ten-mile transport "missing link" for rail services in western Sydney, where immigration and economic issues are worrying voters.

Transport minister Anthony Albanese said the project was vital for the economic development of Australia's biggest city.

"This is an important project for Sydney that links two major economic hubs (of the city) that will have a transformative impact on Sydney," he said.

Party strategists from both sides believe the election will be decided in a handful of marginal seats in Queensland and New South Wales, where border security, population growth, infrastructure and economic issues are worrrying voters.

"This election will be decided in fewer than 30 seats," The Australian's political editor Dennis Shanahan wrote.

Ms Gillard retains a strong advantage as preferred prime minister with 49 per cent support to 34 per cent for conservative leader Mr Abbott, although he was closing the gap in Queensland, where they are now level. Labour won in 2007 with 52.7 per cent of the vote against 47.3 per cent for the conservatives.