Earlier, a lycra-clad Mr Abbott was reluctant to answer reporters' questions as he prepared to cycle from Parliament House to nearby Narrabundah for the launch of the annual Pollie Pedal charity ride. Opposition Leader Tony Abbott speaks at the No Carbon Tax rally outside Parliament House in Canberra. Credit:Andrew Meares Mr Abbott yesterday spoke to the Canberra rally in front of placards with slogans such as "Ditch the witch", while one banner labelled Prime Minister Julia Gillard "Bob Browns [sic] bitch". Both the government and the Australian Greens have called on Mr Abbott to apologise to Ms Gillard for appearing to endorse the derogatory sentiments of some protesters outside Parliament House. Mr Abbott urged "everyone inside and outside the Parliament" to conduct the carbon tax debate with respect.

"If the Prime Minister had been straight with the Australian people before the election, we wouldn't be in quite the situation we are now in," he said. Protesters at the No Carbon Tax rally outside Parliament House in Canberra. Credit:Andrew Meares Climate Change Minister Greg Combet earlier demanded Mr Abbott disassociate himself from the protesters' behaviour in a more formal manner, saying some of the slogans and placards were extremely offensive. "I really think he needs to do that in a decisive way ... He needs to apologise for being associated with it," he told ABC Radio today. Mr Abbott would not indicate whether he would apologise to Ms Gillard when the pair meet later today to discuss the federal intervention in Northern Territory indigenous communities.

Opposition MPs defended their leader today, with one frontbencher accusing the government of double standards. The amazing thing for me is that politicians of such experience as Tony Abbott and his senior colleagues ... did nothing about the banners. "The ALP website right now is comparing Tony Abbott with a Nazi war criminal," climate change spokesman Greg Hunt told ABC Radio. Another Liberal frontbencher, Sophie Mirabella, said the rally was an expression of people power. "The reason so many were angry was that they felt they had been lied to," she said, referring to Ms Gillard before the election saying she would not introduce a carbon tax.

Most of the protesters were "ordinary and normal" people who had been demonised by the government to keep them quiet. "They are not going to be shut up by the glib spin of the Prime Minister and Mr Combet." Ms Mirabella defended the use of the word "liar" to describe Ms Gillard, but baulked at defending the use of "bitch" to describe her. Senator Brown, who has written to the Prime Minister expressing his disgust at the behaviour of some protesters, said the posters were "particularly offensive, really quite disgusting". "The amazing thing for me is that politicians of such experience as Tony Abbott and his senior colleagues ... did nothing about the banners," he told ABC Radio.

"They took them as part of the ambience." Mr Abbott, having had time to reflect on it, owed Ms Gillard an apology, Senator Brown said. Senior Nationals senator Barnaby Joyce said the vast majority of people at the rally were "mums, dads, grandparents, aunties and uncles". "They were doing it because they were furious, because they were misled and lied to and I will stand by them," he told reporters in Canberra. "To have them once more, today, ridiculed by this Labor Party is contemptible."

However, Senator Joyce, who spoke at the rally, said he did not endorse some of the placards. One Labor MP yesterday likened the rally to a convention of Dungeon and Dragons enthusiasts. Senior Liberal senator Eric Abetz said Mr Abbott had no reason to apologise. "He was not the author of the signs," he told reporters, adding that the author of the signs should apologise. "I personally saw the sign and I know one of the organisers also asked for those two people to move and they did not. That is an unfortunate situation."

Senator Abetz said Senator Brown was being hypocritical in asking for Mr Abbott to apologise to Ms Gillard. "If you are asking me if Senator Brown talks with a forked tongue to the Australian people, unfortunately he has a record in doing so on a regular basis," he said. Loading AAP Follow Environment on Twitter