Chris Eubank Jr's scheduled bout with Conor Benn has been postponed after the latter returned a positive drugs test.
On Wednesday, it emerged 26-year-old Benn had tested positive for the banned substance clomifene last month.
The British Boxing Board of Control (BBBofC) subsequently prohibited the fight from taking place, though promoters on both sides attempted to force a U-turn.
However, their efforts were unsuccessful, with the fight now officially postponed.
"After discussions with various parties, we have taken the decision to formally postpone the bout between Chris Eubank Jr. and Conor Benn," a joint statement from the promoters read on Thursday.
"It is undeniable that the BBBofC's decision to withdraw their sanctioning was procedurally flawed and without due process. That remains a legal issue between the promoters and the board which we intend to pursue.
"However, whilst there are legal routes to facilitate the fight taking place as planned, we do not believe that it is in the fighters' interests for those to be pursued at such a late stage, or in the wider interests of the sport.
"As promoters, we take our obligations and duties very seriously, and a full investigation will now need to take place. We will be making no further comment at this time and news for ticket holder refunds will follow."