BEIJING, Dec. 19 -- China's double Olympic champion Sun Yang has been under fire since the news broke that he had served a doping ban earlier this year.

It was the most shocking news of Chinese swimming in 2014 and has caught world-wide attention.

The star swimmer has been barred from training in Australia and his Australian coach Denis Cotterell isn't allowed to coach Sun as a result of the new policy to be implemented by Swimming Australia.

The Chinese Swimming Association (CSA) announced last month that it had banned Sun for three months from May 16 to Aug. 17 as he had tested positive for the banned stimulant trimetazidine during the national championships in May.

The CSA believed in Sun's innocence and said Sun had offered enough evidence to prove he had no intention to take the drug to improve his performance.

Sun's national 1,500m freestyle title was stripped.

He took part in the Asian Games in September and collected three gold medals in the men's 400m free, 1,500m free and 4x100m free relay.

The World Anti-Doping Agency has decided not to appeal against a three month ban imposed against Sun but has warned China of the way it handled the case.

"WADA has written to CHINADA (China Anti-doping Agency) however, raising its concern over the delayed public reporting of the case," a WADA spokesman wrote to a world news agency on Wednesday.

Judging by results alone, Sun Yang was overshadowed by the 21-year-old Ning Zetao, who broke the Asian record to win the men's 100m freestyle and also took the 50m free, 4x100m free relay and 4x100m mixed relay in Incheon, South Korea, where China topped the swimming table with a 22-12-11 record.

Ning went on to improve the 100m Asian record to 47.65 seconds in a national meet in October, which was the second fastest time of the year and could have won him a gold in last year's Barcelona world championships.

Xu Jiayu claimed two silvers at Incheon in the men's 100m and 200m backstroke. He renewed the national 100m back mark to 52.34 seconds in May and the time was the world fastest of the year.

Good results also came from young women swimmers. Shen Duo, 17, clinched four Asian Games golds in the women's 100m, 200m free and 4x200m free relay and 4x100m free relay after sweeping six golds at the Youth Olympic Games in Nanjing.

Chen Xinyi, 16, won the women's 100m butterfly and 50m freestyle in Incheon. Her winning time of the fly ranked third of the year.

Shi Jinglin, a breaststroke specialist, won the women's 100m at the Asian Games.

Double Olympic champion Ye Shiwen was not in top form but still won the 200m and 400m medley gold in Incheon.

With top guns absent, China didn't do well in the short-course world championships in December, finishing with two silvers and one bronze.