New Zealand heavyweight boxer Joseph Parker

Wellington (AFP) - Former world heavyweight champion Joseph Parker denied on Saturday taking a prohibited substance, after learning he had failed a drug test on the day of his shock loss to Fabio Wardley.

The 33-year-old New Zealander said on social media it was a “real surprise” to learn of an adverse finding from an anti-doping test taken on October 25.

Parker suffered an 11th-round stoppage defeat by British boxer Wardley and lost his status as WBO mandatory challenger for undisputed heavyweight champion Oleksandr Usyk.

“The Voluntary Anti-Doping Association (VADA) last night informed all required parties that Joseph Parker returned an adverse finding following an anti-doping test conducted on 25 October in relation to his bout with Fabio Wardley,” promoters Queensberry said in a statement.

“While the matter is investigated further, no additional comment will be made at this time.”

Parker said he was confident his name would be cleared.

“Before my recent fight, I took a voluntary test and have now been informed that it returned an adverse result,” he wrote on his Instagram account.

“This came as a real surprise to me.

“I did not take any prohibited substance, I do not use performance-enhancing drugs and do not support their use.

“I am co-operating fully with the process now underway and I am confident the investigation will clear my name.”

UK tabloid The Sun reported that Parker tested positive for cocaine.

Parker had put himself on course for a potential fight against the outstanding Usyk following six successive wins, a sequence including victories over Deontay Wilder, Zhilei Zhang and Martin Bakole.

However, he could now face a ban depending on the outcome of the investigation.

Parker became world champion in 2016 but he lost his WBO belt by unanimous decision to Britain’s Anthony Joshua in Cardiff two years later.