Suggestions from the Australian Christian Lobby (ACL) that a gay lifestyle is more hazardous than smoking caused Prime Minister Julia Gillard on Thursday to pull out from addressing the lobby's national conference in October.

Ms Gillard said it would not be proper for her to address the ACL national conference due to ACL Director Jim Wallace's comment deemed offensive by gay groups.

"There are a range of deeply held views in the community on the issue of same-sex marriage but it is the responsibility of all parties in this debate to be respectful and responsible in any public comments they make," the prime minister said in a statement.

"I believe yesterday's comment by Jim Wallace were offensive. To compare the health effects of smoking cigarettes with the many struggles gay and lesbian Australians endure in contemporary society is heartless and wrong," Ms Gillard said.

Mr Wallace made the disparaging remarks at a debate on same-sex marriage in Tasmania on Wednesday.

"I think we're going to owe smokers a big apology when the homosexual community's statistics for its health - which it presents when it wants more money for health - are that it has higher rates of drug taking, of suicide. It has the life of a male reduced by up to 20 years," Mr Wallace was quoted by The Age.

He pointed out that smoking reduces the life of a person by seven to 10 years.

Mr Wallace comments led Australian Marriage Equality convener Alex Greenwich to ask the prime minister to reconsider her addressing the ACL national conference. Ms Gillard is against same-sex marriage personally, but would allow Labor members a conscience vote on the issue.

Initially the prime minister's office said Ms Gillard is invited to speak at different events and her presence should not be taken as an endorsement of the views of the event organiser.

However, prospects of losing gay votes at a time when the Labor Party is beginning to regain the trust of Australians apparently made the prime minister go for a U-turn.

"Although everyone is entitled to their own views, these statements reiterated again today on behalf of ACL are totally unacceptable. In light of this, I believe my attendance at the conference would be inappropriate," Ms Gillard said.

Mr Wallace insisted his comments were misrepresented by gay activists in a bid to demonise him and win the debate over same-sex marriage.

"I was not comparing homosexuality with smoking at all. What I was saying is that on one hand we are vocal on our discouragement of people to smoke and on the other we are suppressing public dialogues about the health risks associated with homosexuality," The Herald Sun quoted Mr Wallace, who pushed for more open and honest debate before the Parliament about the issue rather that vitriol from speech suppression from gay activists.

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