Three coalition MPs who say that gay marriage infringes the rights of civil celebrants and children have been labelled 'bigots'.
A trio of government MPs arguing gay marriage infringes human rights have been labelled "bigots scraping the bottom of the barrel".
A private cross-party bill that aims to legalise same-sex marriage has been given the tick of approval by parliament's human rights committee but not by coalition members Michael Sukkar, David Gillespie and Matthew Canavan who say it infringes the rights of civil celebrants and children.
"The bigots are scraping the bottom of the barrel," Greens MP Adam Bandt told reporters in Canberra.
Mr Sukkar said the coalition had committed to a plebiscite but warned the protection of fundamental human rights could not be outsourced to the ballot box.
"The right to freely practise religion must be protected as a fundamental building block of our free and open society," he said.
Senator Canavan is adamant there are genuine human rights problems in the bill.
"I don't think any Australian, including celebrants, should be forced to do anything against their religious views," he told reporters.
"There is no basis for this in international human rights law."
Labor MP Terri Butler, a co-sponsor of the bill, said the trio were "living in a parallel universe" with their argument.
Greens senator Robert Simms also slammed the coalition MPs for "cloaking bigotry and homophobia in the language of human rights".
Senator Simms has launched a postcard as part of his campaign for same-sex marriage that photoshops Prime Minister Malcolm Turnbull and his predecessor Tony Abbott onto the movie poster for blockbuster comedy Wedding Crashers.
"We have two wedding crashers in the coalition preventing progress on this reform: Tony Abbott and now Malcolm Turnbull," he said.