Martina Hingis, who won five Grand Slams, is no stranger to controversy. This time, she is embroiled in another mess as the estranged husband of the tennis star claims she is a serial adulterer.

Hingis was having a wonderful time, having helped the Washington Kastles of World Team Tennis make history and being inducted into the International Tennis Hall of Fame in Rhode Island. But her estranged husband has put the spotlight on their personal life.

Thibault Hutin, a 26-year-old Frenchman who is an equestrian show jumper, says that he knows of at least two times that Hingis, 32, cheated during their marriage, according to a Swiss newspaper. Hutin said he suspects it’s more, calling Hingis a serial cheater.

“She has always been like that… I think she has always been unfaithful to her boyfriends. She is a serial cheater.

“A year after the wedding, we were supposed to meet in New York and I wanted to give her a surprise. Upon arriving at the hotel room it was me that was surprised, because Martina was not alone.

“Late last year, I found out that she had cheated on me again.

“Martina has a very personal conception of morality,” said Hutin, who says he learned that Hingis had announced their separation on Monday when she released a statement to a Swiss magazine.

Hingis is now reported to be in a relationship with David Tosas Ros, a Spanish sports management executive, according to the report.

“They shared the hotel room there and they paraded themselves in public in the Bois de Boulogne,” Hutin said. “There are even pictures of them. You can imagine how painful it was for me.”

Hingis was ranked No. 1 in women’s tennis for 209 weeks during her career, which began when she was 15, peaked when she appeared in all four Grand Slam finals in 1997 — winning three — and was interrupted in 2002 by recurring ankle injuries and back pain that led to an early retirement at 22. She didn’t win another major after returning to full-time play in 2005.

“I want to play tennis only for fun and concentrate more on horse riding and finishing my studies,” she said in 2002.

Hingis retired in November 2007 after she was told that there was an investigation into alleged cocaine use after she tested positive for benzoylecgonine, a metabolite of the drug, during Wimbledon. Although she maintained her innocence, she was banned from play for two years.

“I have tested positive but I have never taken drugs and I feel 100 per cent innocent,” she said at the time.

On being inducted into the International Tennis Hall of Fame, she said: “It is a tremendous honour. It is truly a privilege to be part of such an exclusive group of tennis icons.”

Hingis owns a slew of “youngest ever” records. She was already the youngest player to win a junior Slam (the French Open at 12) when she became the youngest Slam champion by teaming with Helena Sukova to win the 1996 Wimbledon doubles title at 15 years, 9 months.

She was also the youngest to reach No. 1 in singles; she ascended to the top as a 16-year-old in 1997, when she won the Australian Open, Wimbledon and the US Open and lost to Iva Majoli in the French Open final.