Atletico Madrid have released an official statement accusing Barcelona of 'disrespect' for what they deem to be an illegal pursuit of Antoine Griezmann.
Talk of Griezmann's impending move to the Nou Camp has been rumbling on for several months and, on Friday afternoon, Barcelona president Josep Maria Bartomeu confirmed that the club were interested in signing the 28-year-old.
At his press conference, Bartomeu insisted that Barcelona had only began talks with Griezmann this week, but widespread reports have claimed the Frenchman signed a pre-contract agreement with the La Liga champions back in March.
Barca expect to pay €120m (£107m) for Griezmann after the forward's buyout clause dropped down from €200m (£180m) on July 1.
While Atleti have landed a ready-made replacement in Joao Felix, the club are set to request charges be brought against Barcelona for contacting Griezmann without their permission.
The statement accused both Barcelona and Griezmann of 'disrespecting' Atletico Madrid and their supporters.
'On May 14, Antoine Griezmann informed Miguel Angel Gil, Diego Pablo Simeone and Andrea Berta of their decision to leave the club at the end of the season,' Atletico's statement said.
'In the days following that meeting, Atletico Madrid learned that Barcelona and the player had reached an agreement last March, specifically in the days after the second leg of our Champions League tie against Juventus, as well as they had been negotiating the terms of the agreement since mid-February.
'In reference to Bartomeu's statement made today, we want to state that it is true that yesterday there was a meeting between Miguel Angel Gil and Barcelona CEO Oscar Grau at the request of Barcelona and that at that meeting, Mr. Grau expressed his intention, once the clause of rescission of the contract of Antoine Griezmann and have passed from €200m to €120m, request a postponement of the payment of the aforementioned amount of the current clause as of July 1.
'Obviously the response from Atletico Madrid was negative, understanding that both Barcelona and the player have disrespected Atletico Madrid and all its fans.'
Atleti have demanded that Griezmann report back for pre-season training next week despite the France international declaring that he was leaving the club back in May.
'As a result of all this, today, Atletico Madrid has requested the player, his sister as agent of the footballer and his lawyer, that Antoine Griezmann, in compliance with their contractual obligations with our club, appear next Sunday in order to start pre-season with the rest of his teammates,' the statement continued.
'Through this press release, Atletico Madrid wants to express its strongest repulsion for the behavior of both, especially Barcelona, for having induced the player to break his contractual relationship with Atletico Madrid at one point during the season where the club was playing, not only the Champions League tie against Juventus, but the League title against Barcelona itself.
'That is something that we consider violates protected periods of negotiation with players and alters the basic rules that govern the integrity of all sports competition, besides being a huge loss to our club and its millions of fans.'