At an event marking National Marriage Day, organised by his sister, Senator Heffernan had an altercation with three civil union activists.

The activists' group, Equal Love, later issued a press release accusing Senator Heffernan of allegedly saying to them: ''I don't mind gay people, I just want you to stop f---ing the kids."

Senator Heffernan denied using those exact words.

''Everyone knows where I stand on protecting the institution of marriage and prosecuting the rights of the gay community,'' he told the Herald.

''Everyone knows that I conduct a continuous war on people who use kids as sex objects and I don't intend to change now.''

The controversy will not help Senator Heffernan's bid to shore up his preselection before the federal election, due next year.

It was also an unwelcome distraction for Mr Turnbull, whose inner Sydney seat of Wentworth has a large number of gay and lesbian residents.

A spokesman for Mr Turnbull last night declined to comment.

Senator Heffernan's day grew worse when he was caught on camera making an obscene gesture during question time. The Government Leader in the Senate, Chris Evans, complained that Senator Heffernan had made the gesture at the Climate Change Minister, Penny Wong.

But Senator Heffernan said he had meant it for the West Australian Labor senator Glenn Sterle.

''I apologise to Senator Sterle; he knows I was sending him an obscene message,'' Senator Heffernan told the Senate.

Senator Heffernan later told the Herald that the pair had a friendly rivalry as members of the Senate's agricultural committee.