According to the agency, Sun tested positive for the banned stimulant trimetazidine which is used to treat angina.

The drug was added to the World Anti-Doping Agency's (WADA) Prohibited List in January.

"I have taken many doping tests during years of training and competition and I had never failed one before," said Sun.

"I was shocked and depressed at that time, but at the same time it made me cherish my sporting life even more.

"I will take it as a lesson and be more careful in the future."

Sun tested positive on May 17 during the National Swimming Championships and had been banned for three months, until August 16, according to Chinese news outlet Xinhua.

He was also fined 5,000 RMB (£520/$816/€656) while officials from his provincial swim team were also handed unspecified penalties.

"Sun Yang in this matter was not completely responsible and the positive test is his mistake, but the mistake is not very serious or negligent," Chinada deputy director Zhao Jian said.

"Because of this, the three-month ban is reasonable."

Sun Yang served his ban in time to return for the Asian Games in Incheon where he picked up three gold medals ©Getty Images



Sun gave up the chance to have the B-sample tested but defended himself in a July hearing where the experts decided to hand him a three-month ban.

He claimed that he used the drug for medical reasons and had been unaware that it was listed in WADA's 2014 prohibited list.

The suspension was served in time for Sun to compete at the 2014 Asian Games in Incheon, where he won three gold medals and a silver.

No mention of the suspension had been made during or prior to the Asian Games with Chinada explaining that it did not immediately announce the sanction because it only reveals positive tests every three months.

"Sun is the most famous athlete in China and is known in the world, which means we need to handle his case very cautiously," said Zhao.

"This is huge bad news but we will not cover it up.

"We announce positive cases and test statistics in our quarterly reports just as WADA requires."

Sun became the first male swimmer from China to win gold at the Olympic Games after taking the 400 and 1500 metre titles at London 2012.

Despite being a national treasure, Sun has proved a controversial figure in recent times.

Last year he was held for seven days in police detention for colliding with a bus while driving his Porsche without a licence.

He also reportedly fell out with his coach over a relationship with a flight attendant and faced a suspension for missing practice in order to make commercial appearances and spend time with his girlfriend.

Following his failed doping test, Sun was stripped of his 1500m national title.

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