Former world number one Martina Hingis announced her retirement from top-flight tennis on Friday.

The 22-year-old "Swiss Miss" who topped the world rankings for four consecutive years, revealed she has lost her battle against severe ankle problems.

"A return to competition is unforeseeable, and I have no plans to ever return," Hingis has told French sports newspaper L'Equipe.

"It's over for me but life goes on. I am not capable anymore of doing what's needed to be done to stay at the top.

"I have been at the top for long enough to know exactly what is required, and I am incapable of it.

"When you have been world number one for four years you cannot content yourself with less.

"I don't want people to feel sorry for me - I have a great life. Even without competition, I am happy.

"I am 22 and my whole life is ahead of me. What I am experiencing is nothing dramatic. The only thing I cannot do anymore is remain competitive."

But Hingis did leave open a small possibility of a return to the circuit sometime in the future.

"I am not coming back - not for now anyway - that is sure and definite."

Hingis took over at the top of women's tennis in 1997 when she won three of the four Grand Slams, only missing out at Roland Garros.

Her victory in the Australian Open, aged just 16 years and three months, made her the youngest Grand Slam singles winner in the 20th century.

Between 1997 and 1999 she won three Australian Opens, one US Open and a Wimbledon title.

Hingis first underwent surgery on her right ankle in October 2001. Seven months later she needed a similar operation on her left ankle.

She fought her way back and reached the 2002 Australian Open final but lost to the then world number one Jennifer Capriati.

Hingis has not won a Grand Slam for nearly three years and in October she slipped out of the world top 10 for the first time in six years.