World heavyweight boxing champion Tyson Fury is suing Britain's anti-doping and boxing authorities over allegations that he used the performance-enhancing drug nandrolone.
The legal team for the both Fury and his cousin, Hughie, who was also accused, said "Team Fury" had issued proceedings in the High Court.
"The two boxers strenuously deny taking any performance-enhancing drugs. However, during the last five weeks, leaks about these charges have appeared in the press and both boxers have been the targets of continual abusive language on Twitter," lawyer Lewis Power said in a statement.
The Sunday Mirror reported on 26 June that traces of the banned substance nandrolone were found in a urine sample taken from Fury in April 2015 by UK-Anti-Doping, the body used by the British Boxing Board in the UK for random blood and urine testing of its licensed boxers. The test in question was in fact in February 2015.
The 27-year-old denied the claim at the time and his legal team said on Tuesday that the result of further tests from March and May in 2015 were contradictory.
UKAD have not made the test public at any point and declined to comment. Fury's legal team said an interim judgment was expected before Fury's rematch with the Ukrainian, expected to be in October.
It is a re-match between the pair after Fury beat Klitschko, 40, in November 2015 to win the WBA and WBO heavyweight titles.
The Daily Telegraph understands Fury has been tested multiple times in the last eighteen months with no adverse findings, while Peter Fury, trainer to Tyson Fury and the father of Hughie Fury, told Boxing News in a recent interview that they believe that there is "a witchhunt" against his nephew.
Michele Verroken, director of the company Sporting Integrity and former head of UK Sport's anti-doping unit, told The Telegraph that nandrolone has created grey areas in the past when such a thing known as "false positives" occur, when traces of nandrolone can increase above normal levels when athletes are in high-intensity periods of training, or from certain meats such as boar.