Thousands of people have marched through central Sydney to protest against the carbon tax introduced by the Australian government on Sunday.
Many are calling for an early election.
The opposition has pledged to repeal the act if it wins next year's general election.
From 1 July, around 500 businesses will be made to pay $A23 for every tonne of pollution they produce. They say they will have no choice but to pass on the cost to customers.
To mark the day, the opposition is rolling out an advertising campaign that highlights Prime Minister Julia Gillard's policy reversal: she announced before the 2010 election that there would be no carbon tax under a government she led.
However, the ABC reports the government is announcing extra payments and incentives as a further attempt to counter any carbon tax pain.
More than seven million people will get a tax cut and some low-income family payments will be boosted.
Businesses will also get relief in the form of offsets to tax losses against previous tax they have paid over the past two years and an instant asset write-off.
Climate Change Minister Greg Combet says the carbon tax is "the right thing to do". But National leader Warren Truss says the carbon tax has already hurt business confidence and it comes at the worst possible time.
Opposition leader Tony Abbott says the next federal election will be a referendum on the carbon tax. He again pledged on Saturday to abolish the carbon tax if he wins government.
''The next election will be a referendum on the carbon tax. It will be a referendum on prime ministers who tell lies'', he said at a conference of the Liberal Party in Melbourne.
