Richard Williams also says that his other daughter, Serena, should devote more attention to her studies to avoid becoming "one of the dumbest athletes in the world".

As Venus and Serena gear up for the WTA Tour event in Amelie Island, Williams Snr told a Florida newspaper that 21-year-old Venus should focus her energies more on business interests.

"I told Venus two or three years ago that she should retire. I really think she should," said Williams.

The elder Williams sister is currently ranked second in the world but her father believes she should be concentrating on her other talents.

"Venus is a rare human being when it comes to education, business and business knowledge," he said.

"She is a rare quality that every now and then you see in life. I've tried to get Venus to understand that."

She is currently taking classes via the Internet, working toward a degree in fashion design from the Art Institute of Fort Lauderdale.

While Williams Snr did not advocate a complete career change for 20-year-old Serena, he did say she needed to pay more attention to non-tennis matters.

"I think Serena puts a little too much emphasis on tennis. And if she keeps that up, she can turn out to be one of the dumbest athletes in the world," he said.