Australia unveiled plans Sunday to force its 500 worst polluters to pay $25 for every metric ton of carbon dioxide they emit.

The government said the highly unpopular carbon tax will take effect on July 1 of 2012 and will continue until the country shifts to an emissions trading mechanism, with prices set by the market.

Opponents of the tax say it will harm industry, send jobs offshore and increase the cost of living for ordinary Australians.

But Prime Minister Julia Gillard told reporters that Australians will be compensated for the cost through government family payments, pension boosts and income tax cuts.

The prime minister says she has the numbers in parliament to pass the legislation, but her popularity has plummeted in opinion polls since she announced plans for the tax earlier this year.

An AC Nielsen poll released last month showed that only 27 percent of voters say they support her Labor party, the lowest vote for a major party in the poll's 39-year history.