British boxer Amir Khan has been handed a two-year ban from all sport after a test detected the prohibited substance ostarine following his fight against Kell Brook last February, the UK Anti-Doping agency said on Tuesday.

Former light-welterweight world champion Khan, 36, announced his retirement in May after his sixth-round stoppage defeat to compatriot Brook on Feb. 19 but would now be unable to return to the ring until April 2024.

The UKAD website states that ostarine is a drug designed to have similar effects to testosterone. It is present on the World Anti-Doping Agency's prohibited list as an anabolic agent and is prohibited in sport at all times.

Khan, who had expressed concerns over a lack of drug testing before his fight against Brook, accepted that he broke anti-doping rules but said it was not intentional.

An independent tribunal accepted Khan's argument and ruled out "deliberate or reckless conduct" in a written decision dated Feb. 21, 2022, and imposed a two-year ban from all sport due to "strict liability."

"Strict liability means Athletes are ultimately responsible for what they ingest and for the presence of any prohibited substances in a sample," UKAD chief executive Jane Rumble said.

Khan maintained his innocence in an interview with Sky News on Tuesday, saying: "I've never cheated in my life.

"You can see by my performance against Kell Brook... I lost the fight. If I went in there and knocked Kell Brook out it's different."

Khan also added that "the amount in my system could have been by shaking people's hands".

Khan (34-6, 21 KOs) was Olympic lightweight silver medallist at the 2004 Athens Games at 17 years old and went on to win the WBA light-welterweight belt from Ukrainian Andriy Kotelnyk in 2009 and added the IBF title in 2011 when he beat American Zab Judah.

Khan's ban began on April 6, 2022 and will expire on April 5 next year.