Opposition Leader Tony Abbott has addressed a large crowd of anti-carbon tax protesters outside Parliament House, telling them the carbon scheme is "based on a lie" and will not work.

But he avoided the embarrassment he suffered in March when his speech to a similar rally was in front of a placard reading, "JuLiar, Bob Brown's Bitch".

This time, organisers used a large banner reading "stop carbon lies" as a backdrop to the speakers.

In March, the Government accused the rally of being largely made up of "extremist" elements, including Pauline Hanson and her supporters, as well as far-right groups such as the League of Rights.

At today's rally Mr Abbott, who was greeted with chants of "Tony, Tony" as he took the stage, was quick to distance himself from some of the people and the placards in the gathering.

"I can see a lot of people I agree a very great deal with; I can see some people I don't agree with on everything," he said.

"I can see a lot of signs. Some signs I agree with; some signs I don't necessarily agree with.

"There are two things we all want to say today. First, we don't want a carbon tax. And second, we do want an election."

While he was speaking, pall-bearers placed two coffins in front of the crowd, one reading: "Our democracy is dead" and the other: "Julia, you are killing our country".

The rally was organised by a group calling itself the Consumers and Taxpayers Association and is publicised and supported by Sydney radio station 2GB.

Addressing the rally, Nationals Senate Leader Barnaby Joyce said the anti-carbon tax movement is at "half time and we're still going".

"Last time they called you deniers. You were oddballs. You were Ku Klux Klan members. You were rednecks. Then in the New South Wales election you were voters and you tossed them out," he said.

Climate Change Minister Greg Combet says he has not considered addressing the rally - nor has he been invited.

"If it's anything like the last one I wouldn't want to appear there," he told ABC's Radio National.

Mr Combet said during his winter break five-week campaign, where he travelled the country selling the carbon tax, he found a lot of concern "whipped up by Tony Abbott's completely unprincipled opportunistic fear campaign".

Greens leader Bob Brown likened the rally to the right-wing tea party movement in the United States.

"This is whacky Tony Abbott, Tea Party-style politics, but that's part of the marble of democracy, and 2GB, a great big joke, but they've got people going, and good on them," he said.

Meanwhile, federal independent MP Bob Katter has told a rally at Parliament House same-sex marriage should not be taken seriously and deserves to be ridiculed.

Mr Katter is amongst a handful of federal MPs who addressed a gathering of several hundred people attending the pro-marriage rally today.

All state and territory divisions of the ALP, with the exception of New South Wales, have passed motions of support for full marriage equality.

Labor MP John Murphy also attended, telling the anti-gay marriage rally he will ignore opinion polls and fight to make sure gay people will not be able to marry in Australia.

A recent opinion poll found almost two-thirds of Australians support gay marriage and the issue will be debated at the ALP national conference in December.

But Mr Murphy told the rally his Western Sydney electorate of Reid does not want gay marriage and he will campaign against it.

"I have no doubt that there is a silent majority - not only in my own electorate, but beyond - who want us to stay firm and defend the institution of marriage. I will do that," he said.