Japan's main horse racing governing body on Friday announced the retirement of its most successful female jockey, Nanako Fujita, following her suspension for taking a smartphone inside a restricted area of a racecourse.

The Japan Racing Association accepted the 27-year-old's retirement after it was discovered she had used a smartphone in the area where jockeys are banned from using communication devices to prevent them from having contact with the outside world before a race.

The ban is intended to prevent the illegal sharing of information that could affect the integrity of the sport, which allows betting on races.

Fujita is alleged to have brought her smartphone inside the rooms and used it to communicate on multiple occasions through April last year.

Fujita has won 166 races at JRA meets, more than any other woman. She made her JRA debut in 2016, becoming the first woman to join the ranks in 16 years.

She notched her personal-best 43 wins in a year in 2019, the same year she became both the first woman to win a JRA graded stakes race and compete in a G1 race. Fujita won six times this year.