PRIME Minister Julia Gillard has rejected claims small businesses will be hurt by the carbon emissions tax.
It comes as one of the nation's richest men flagged a High Court challenge against the incoming pricing regime.
Mining magnate Clive Palmer's lawyers are investigating possible grounds to challenge the carbon tax laws, which passed parliament in November.
Opposition Leader Tony Abbott said there appeared to be constitutional problems with the laws, which the coalition plans to rescind in government, particularly in relation to how the tax impacts on states.
"If Clive Palmer has got solid legal advice that there are constitutional problems, he has every right to bring an action before the High Court," he told reporters in Canberra yesterday.
Ms Gillard said the government had taken "very careful" legal advice when designing its carbon pricing scheme, which comes into effect on July 1.
"The interesting thing here is Clive Palmer says something one day and Tony Abbott parrots it the next," she said.
Mr Palmer said in a statement he was "disappointed" at the prime minister's attack.
"They think I am a threat to democracy - well I think I am epitomising what democracy is all about," he said.
"Our founders set up the constitution for all people to have rights - it wasn't set up for minorities to be persecuted."
The prime minister came under fire in parliament over the impact of the carbon tax on small businesses.
To underline the attack, senior Liberal MP Tony Smith brought into the chamber a plastic plant pot labelled "No carbon tax - plant a tree instead" from a Victorian small business he said would face a $320,000 power bill.
Another Liberal MP Jane Prentice said the carbon tax would impact on school bus ticket prices.
Ms Gillard challenged Mr Abbott to support the minerals resource rent tax and its associated corporate tax cuts as a way of supporting small business, rather than running a "fear campaign" over carbon pricing.
She said the carbon tax would directly impact on fewer than 500 big companies, and consumers - including the "mums and dads of the children on the bus" - would be compensated through tax cuts and payment rises.
"The policies and plans of the leader of the opposition are a disgrace for those working families because they are all about placating billionaires," Ms Gillard said.
The coalition also seized on a report that shopping centre giant Westfield is introducing a charge clause in lease agreements for its 12,000 onsite retailers to offset the impact of the carbon tax.
"In every shopping centre, in every shop all around Australia, it is the small businesses that will pay and it is the mums and dads and pensioners who will pay," opposition environment spokesman Greg Hunt said.
But Ms Gillard said the Shopping Centre Council of Australia (SCCA) had confirmed the clause had been introduced when the Howard government first flagged an emissions trading scheme.
Opposition small business spokesman Bruce Billson said the coalition would cut taxes for the sector, but wanted to ensure they went not only to incorporated businesses but the two-thirds of small businesses that were not structured that way.
"We will make a modest cut (to corporate tax), but we are working through what the scale of that will be," he said.
He said the instant asset write-off proposed by the government also had "appeal", but should not be dependent on a mining profits tax.