Tony Abbott has forced the resignation of his parliamentary secretary, the right-wing South Australian Senator Cory Bernardi, after Bernardi compared gay marriage to bestiality in the Senate debate over the same-sex marriage bill, and then repeated the comments on radio this morning.

The resignation comes after Malcolm Turnbull (who dismissed Bernardi when he was opposition leader for his attack on rival SA Liberal Christopher Pyne) savaged him, describing his comments as hysterical, alarmist and offensive.

Abbott couched the issue in terms of discipline, insisting Bernardi had been “undisciplined”, but agreeing in response to questions that many people would find them “repugnant” and that he didn’t want Bernardi to “dabble” in the area again.

Bernardi told the Senate last night “these creepy people say it is okay to have consensual s-xual relations between humans and animals. Will that be a future step? In the future will we say, ‘These two creatures love each other and maybe they should be able to be joined in a union’.”

Bernardi has repeatedly expressed extreme views on issues such Muslim Australians and climate change — and at each spray, some of the Coalition’s more centrist MPs have grumbled about the need for Abbott to pull him into line and the damage done to the party’s reputation. Until now, Abbott hasn’t — and some MPs thought that was because, privately, Abbott tended to agree with Bernardi. This move today is a victory of sorts for Turnbull over Abbott.

The controversy continues a bad period politically for Abbott, who has come under increasing pressure over his performance and claims about his behaviour as a student. Nonetheless, Abbott has skilfully used the removal of Bernardi to take some pressure off another long-running problem, his talented backbench and the lack of opportunities for promotion. Abbott has promoted two of his stronger backbenchers: Arthur Sinodinos to replace Bernardi as his parliamentary secretary, and Jamie Briggs has finally been promoted, to parliamentary secretary for Families.

“This will make a strong team stronger,” said Abbott, correctly. Bernardi was an extremist and a liability, and his removal per se improves the Coalition frontbench; that Sinodinos and Briggs get to step up is a bonus.