I'd cross the floor on gay marriage: Liberal MP

Openly gay Liberal MP Trent Zimmerman says he would cross the floor in favour of same-sex marriage.

"If a substantive bill came before the parliament, then yes I would cross the floor if the party instructed me otherwise," he said.

Mr Zimmerman said he was concerned about a plebiscite on gay marriage and his personal preference, had he been in the party room earlier, would have been for a free vote and for parliament to decide the issue.

If the costs of a plebescite blew out there would be a "great deal of anger" within the community.

Mr Zimmerman also slammed a coalition colleague's comments on the Safe Schools program.

He said Nationals MP George Christensen's comments likening the gay and lesbian-focused anti-bullying program to pedophile grooming was deliberately inflammatory.

"Some of the language that's been used has been unfortunate ... we have seen a tenor of language used which has been completely unjustified," he said.