Tennis legend Margaret Court reignited controversy over her views on homosexuality on Wednesday as she defied gay protest threats by visiting the Australian Open.

Activists have launched a Facebook campaign against the Australian, whose 24 major singles titles are a world record, and said they would rally at Melbourne Park against the former player, now a church pastor.

But Court took her seat as a spectator at the event on Wednesday, the same day that she repeated her views in an uncompromising opinion piece published in Melbourne's Herald Sun newspaper.

"Let me be clear. I believe that a person's sexuality is a choice. In the Bible it said that homosexuality is among sins that are works of the flesh," she wrote.

"It is not something you are born with. My concern is that we are advocating to young people that it is OK to have these feelings."