Australian Prime Minister Kevin Rudd has called for a Labor caucus vote on his leadership and faces a challenge from deputy leader Julia Gillard. If successful, she will be the country's first woman prime minister.

The spill, as Australians call a leadership challenge, comes after a precipitous fall in Mr Rudd’s popularity since the beginning of the year.

"I was elected by the people of Australia to do a job," Mr. Rudd told a late-night news conference, adding "I was not elected by the factional leaders of the Australian Labor Party to do a job – though they may be seeking to do a job on me."

Mr Rudd’s imperious style and a series of policy backfires – including a “super tax” on mining company profits and a failed ETS – have proved too much for Labor's right wing and some key unions on the left.

This may give former lawyer Ms Gillard, 48, the necessary numbers to topple Mr Rudd, 52, ahead of a general election later this year – one Labor could lose on current polling.

A recent poll put Labor’s rating at 35% to 40% for the opposition parties, though based on the preferential voting system Labor would win narrowly at 52% to 48%.

The mining tax, which was supposed to be a populist attack on corporate Australia and be spread around as a tax cut for everyone else, has proved disastrous.

Thanks to a highly effective lobbying campaign, the public is now aware of the damage such a tax would make on Australia's credibility as an investment destination.

BHP Billiton and Rio Tinto, for example, have warned that billions of dollars worth of investment are at risk from the 40% profit tax.

Even so, the spill has come as a surprise, with Ms Gillard appearing to be a reluctant challenger, saying only: "I confirm that I will be a candidate in tomorrow's ballot. I haven't got any other statement at this time."

But other reports say she told Mr Rudd she had the numbers and demanded he step down. Instead he chose to have the caucus decide it in a vote this morning at 9am (AEST, 11am NZ time).

Ms Gillard was elected to Parliament in 1998 and holds the portfolios of education, employment and workplace relations.