Swiss tennis star Martina Hingis says she is retiring from the sport after denying that she used cocaine. 

The 27-year-old five-time Grand Slam champion made the revelation Thursday during a news conference to announce her retirement from tennis for the second time and refute a claim that she tested positive for the drug at Wimbledon. 

Martina Hingis announced her retirement for a second time Thursday amid allegations she tested positive for cocaine at Wimbledon.
(Canadian Press)

"I find this accusation so horrendous, so monstrous that I've decided to confront it head-on by talking to the press," she said. "I am frustrated and angry. I believe that I am absolutely 100 per cent innocent."

Hingis, known for her squeaky-clean image and infectious smile, spent 209 weeks as the world's No. 1 player during her career.

She won three straight Australian Open titles from 1997-99 and captured both Wimbledon and the U.S. Open in 1997.

Hingis first retired from the sport in 2003 because of chronic hip and ankle injuries before returning to the courts in 2006. She won three titles since her comeback and climbed her way up to No. 7 in the world in 2006. She is currently ranked No. 19. 

Hingis said she was accused of taking cocaine by "an outsource testing company" during this past year's Wimbledon. She lost to American Laura Granville 6-4, 6-2 in the third round of the grass-court Grand Slam.    

The Swiss star said she was "shocked and appalled" when notified that her urine sample came back positive after the loss to Granville.

Under guidance from her family and management, Hingis said she later underwent a privately arranged hair test, which came back negative for cocaine. The official backup B sample test on her Wimbledon urine sample, however, tested positive for the drug.

Hingis said she hired a lawyer who found "various inconsistencies" with the urine sample and felt she would have a good case to fight the results. However, at 27, she said she wouldn't be fighting the charge. 

"I have no desire to spend the next several years of my life reduced to fighting against the doping officials," she said. "The fact is that it is more and more difficult for me, physically, to keep playing at the top of the game.

"And frankly, accusations such as these don't exactly provide me with motivation to even make another attempt to do so."

With files from the Associated Press