The punishment handed down by the Court of Arbitration for Sport (CAS) was "not contrary to the fundamental principles of the legal order," and Sun’s right to be heard "had not been violated," the Swiss Federal Tribunal ruled.

Sun, winner of the Olympic gold medal in the 400 and 1500 metres freestyle at London 2012 and 200m freestyle at Rio 2016, was ordered by the Court to pay legal costs of CHF15,000 ($16,300/£12375).

CAS banned Sun in June last year for refusing to give a sample to doping inspectors.

The 11-time world champion was originally just warned by the International Swimming Federation (FINA) about his conduct during an attempt to take blood and urine from him after drug testers had made an unannounced visit to his home in September 2018.

It turned confrontational after midnight when he questioned the officials' credentials.

It led to Sun's entourage ordering a security guard to use a hammer to smash the casing of a blood vial so it would not be valid for testing.

The World Anti-Doping Agency appealed to CAS to overturn the FINA tribunal ruling.

The Lausanne-based court reduced its original ban of eight years after the 30-year-old Sun appealed to the Federal Tribunal over alleged bias because the CAS panel chairman had posted anti-China comments on social media.

The new ban of four years and three months, backdated to February 2020, ruled the 1500m freestyle world record-holder out of the re-arranged Olympic Games in Tokyo last year and the 2022 Asian Games in his home city of Hangzhou.

Sun, banned for three months in 2014 for a separate doping offence, will be eligible to return in time for 2024 Olympic Games in Paris, although he will be 32 by then.