HUNDREDS of protesters, mainly 50-years-plus, have used poo jokes to make their point at an anti-carbon tax rally.

About 500 protesters gathered in Sydney to rally against the federal government's planned carbon tax, screaming with approval when broadcaster Alan Jones climbed up onto a stage to criticise Prime Minister Julia Gillard.

"She's going to go down the sewer," the Macquarie Radio breakfast host said, pointing to a poster of Greens leader Bob Brown disappearing into a toilet with the slogan "if it's brown, send it down".

"Go away Julia," Mr Jones said.

"Get out of our lives, we don't want you here. We don't want to hear you and we don't want to see you."

The angry scenes in Martin Place in the CBD were reminiscent of the anti-carbon tax rally that took place outside Parliament House in Canberra in March.

In Sydney there were banners saying "Ditch the witch" and others depicting Ms Gillard as the fairytale story character Pinocchio whose nose grew longer the more he lied.

The crowd were angry about the Labor government's decision to raise the carbon tax in this term of government.

They pilloried Ms Gillard for telling voters during the 2010 federal election there would be no carbon tax under her government.

Rock star Angry Anderson introduced the speakers, which included federal Nationals leader Warren Truss and Nationals Senator Barnaby Joyce.

"It will cost hundreds of thousands of jobs, everyone knows that," Mr Truss said.

Senator Joyce told the crowd they were being held "in contempt" by the government because they dared to hold a different view on the need for a carbon tax.

He said those against a carbon tax were being called names.

"Because you are not wise like them. You are rednecks. You are dungeons and dragons participants...," he said.

"This is what your elected members of parliament are calling you.

"Because you dare to question what they have to say.

"You dare to have a contrary view.

"You dare to stand up and have your own point of view and say, 'I don't agree with you on this one'."

One of the protest attendees, Helge Schmidt, runs a small food-related business in Sydney.

He said his electricity bills had risen by $7500 a year, and he was concerned the carbon tax would be too big a burden on small businesses.

"Small business can't afford it," he said.

Also in the crowd was Angela Liati.

Ms Liati, who was convicted in 2009 of lying to police in an attempt to help former Federal Court judge Marcus Einfeld dodge a speeding fine, was wearing a sticker saying "We voted No Carbon Tax".