Australian tennis champion, Margaret Court, has again condemned transgender athletes, while claiming the devil controlled the media and government, in fiery comments just weeks before she was honoured at the Australian Open.

The 24-time Grand Slam singles winner, now a church pastor, drew fire in 2017 for saying she would avoid Qantas over the airline's support for same-sex marriage, which is now law in Australia following a referendum.

She later claimed, in comments that were widely derided, that tennis was "full of lesbians" and that transgender children were the result of a Nazi-style "plot" to brainwash the minds of young people.

The 77-year-old doubled down on her controversial views regarding sexuality during a sermon at her Perth church at the weekend, which came to light on Monday.

"Children are making the decision at seven or eight years of age to change their sex ... no, just read the first two chapters of Genesis, that's all I say. Male and female," Court said in a video of the sermon.

"It's so wrong at that age because a lot of things are planted in this thought realm at that age, and they start to question 'what am I'.

"And you know with that LGBT, they'll wish they never put the T on the end of it because, particularly in women's sports, they're going to have so many problems.

"You have got young people taking hormones and having changes, by the time they are 17 they are thinking, 'Now I'm a boy and really I was a girl'. Because you know what, God made us that way."

Court also highlighted the difficulty of talking about her religious beliefs, claiming "the devil" had control over the media and government.

"The devil gets in and the media and the political, the education, TV -- he wants to control a nation so he can affect people's minds and mouths," she said.

After her previous comments on homosexuality and gay marriage, high-profile players like Billie Jean King and Martina Navratilova called for the Margaret Court Arena at Melbourne Park -- home of the Australian Open -- to be stripped of her name.

That has not happened and the 50th anniversary of Court's calendar-year Grand Slam will next month be commemorated at the tournament, where she will be a guest of honour.

While Tennis Australia last month agreed to mark her achievement of winning all four majors in the same year, it also distanced itself from the player's views.

"As often stated, Tennis Australia does not agree with Margaret's personal views, which have demeaned and hurt many in our community over a number of years.

"They do not align with our values of equality, diversity and inclusion."

Court used to attend the Australian Open regularly but hasn't shown up since 2017, when the controversy over her views first flared.