Tyson Fury is to sue UK Anti-Doping (UKAD) over allegations he used the performance-enhancing drug nandrolone, according to a statement published today.
It was reported by the Sunday Mirror on June 26 that traces of the banned substance were found in a urine sample that dated back to February 2015.
The report also said that his cousin Hughie, another professional heavyweight boxer, had tested positive.
Fury denied the allegations which it was said were being overseen by UKAD.
His legal team claim the results of tests from March and May 2015 were contradictory, and it was reported by the BBC that they had issued proceedings to the High Court.
"The two boxers strenuously deny taking any performance-enhancing drugs," read the statement from their lawyer Lewis Power.
"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."
It has also been reported that an interim judgement is expected before Fury makes the first defence of his WBO and WBA heavyweight titles in a rematch against Wladimir Klitschko.
The two are scheduled to fight at the Manchester Arena in October after their original date of July 9 was postponed when the champion suffered an ankle injury.
A spokeswoman for UKAD told the Press Association: "UK Anti-Doping will not discuss or disclose details of cases until due legal process has been completed and an anti-doping rule violation has deemed to have been committed, at which point information will be published on our website.
"This is to ensure that the rights and privacy of everyone involved are respected and protected, and to ensure cases are not unnecessarily prejudiced."