Kell Brook (left) beat Amir Khan in sixth round to settle a bitter rivalry between the two fighters at Manchester Arena in February 2022British boxer Amir Khan has been banned for two years after an anti-doping test revealed the presence of a prohibited substance following his fight against Kell Brook in February 2022.
The former light-welterweight world champion tested positive for ostarine.
Khan, who retired from boxing in May, accepted he broke anti-doping rules but said it was not intentional.
An independent tribunal accepted that argument, ruling out "deliberate or reckless conduct" by the 36-year-old.
The UK Anti-Doping (Ukad) websiteexternal-link states ostarine is a drug designed to have similar effects to testosterone.
In October, British sprinter CJ Ujah was banned for 22 months after he tested positive for two banned substances, including ostarine, at the Tokyo Olympics.
"This case serves as a reminder that Ukad will diligently pursue anti-doping rule violations in order to protect clean sport," Ukad chief executive Jane Rumble said.
"Strict liability means athletes are ultimately responsible for what they ingest and for the presence of any prohibited substances in a sample."
The ban from all sport is deemed to have begun on 6 April 2022 and expires on 5 April 2024.
Fellow Briton Conor Benn failed two voluntary drug tests for the female fertility drug clomifene before his cancelled bout with Chris Eubank Jr in October.
Benn was allowed back into the World Boxing Council rankings after it ruled his failed drugs test was not intentional and and could have been caused by a "highly-elevated consumption" of eggs.
However, he remains under investigation by Ukad and the British Boxing Board of Control, and is unable to fight in the United Kingdom as he does not have a boxing licence.
Khan, who won a silver medal at the 2004 Athens Olympics as a 17-year-old, turned professional in 2005.
In 2009 he became world champion, defeating Andreas Kotelnik at Manchester Arena for the WBA light-welterweight title. His win over Zab Judah in 2011 earned him the IBF belt and unified champion status. Khan then lost the titles in his next fight to Lamont Peterson.
He was beaten by Brook via sixth-round knockout in what proved to be his final professional bout.
Khan retired from the sport three months later, finishing his career with 34 professional wins and six losses, having turned professional in 2005.
Outside the ring, he has maintained a strong public profile through his appearances in Australia-based reality gameshow I'm a Celebrity... Get Me Out of Here! and his own BBC reality TV show, Meet the Khans: Big in Bolton.
He is due to make a second appearance on I'm a Celebrity, this time based in South Africa, later this month.
'Ukad announcement adds different dimension to Khan's swansong' - analysis
Coral Barry, BBC Sport
Amir Khan is one of Great Britain's greatest boxers. His silver medal as a 17-year-old at the Athens Olympics in 2004 made him into a household name. He was a world champion, fought the best from Saul 'Canelo' Alvarez to Terence Crawford and his retirement fight against Kell Brook was a typically thrilling end to a storied career.
The Brook fight was 17 years in the making and a huge event that captured the attention of boxing and the wider sports world, despite it being well past its sell-by date. Both men were 35 when the fight happened and have since retired.
Ukad's announcement adds a different dimension to Khan's swansong.
Testing positive on fight night has become more and more unusual considering it is one of the few times a big boxing star can be guaranteed they will be tested.
Khan has been cleared of intentionally ingesting ostarine after a lengthy investigation, but strict liability carries a mandatory two-year ban regardless of intent.
