New Zealand heavyweight boxer Joseph Parker

London (AFP) - Former world heavyweight champion Joseph Parker failed a drugs test on October 25, the day of his shock loss to Fabio Wardley in London, his promoter announced Friday.

The 33-year-old New Zealander suffered an 11th-round stoppage defeat by British boxer Wardley, in a fight concluding shortly before midnight local time, 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.”

An initial report in UK tabloid the Sun said Parker had tested positive for cocaine, but this has not been confirmed.

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