Atlético Madrid have released a statement, saying the €120million paid for Antoine Griezmann in La Liga's offices on Friday afternoon, is not sufficient.
Barcelona officially announced Griezmann as their newest addition today, shortly after his lawyers deposited the money into La Liga's headquarters in Madrid.
But Atletico insist the agreement between Barcelona and Griezmann was reached before his release clause dropped from €200million to €120million on July 1.
"The amount deposited is insufficient to pay his release clause because it's obvious that the agreement between the club and Barcelona was done before his fee dropped from €200 to €120 million.
"Atlético Madrid understand that the contract was broken before the end of last season, on the basis of the facts, actions and statements of the player and the club has therefore started the proceedings it considers opportune to defend its legitimate rights and interests.
"Atleti are disgusted by the behaviour of Barcelona and the player and particularly Barcelona, for inducing a player to break their contractual relationship with Atlético Madrid at a time in the season when the club was playing, not just a Champions League tie against Juventus, but also the League title against Barcelona itself," the statement read.