After a Lamine Yamal goal was disallowed by VAR in Barcelona's 3-2 defeat at Real Madrid, Barcelona coach Xavi Hernandez criticised the officiating in LaLiga, which does not use goal-line technology.
Vinicius Jr and Lucas Vazquez's goals helped Real equalise twice after Andreas Christensen and Fermin Lopez had put Barca ahead on Sunday.
Yamal's effort in the 28th minute was reviewed by VAR for several minutes, as it appeared to cross the line before Real keeper Andrey Lunin cleared it. The goal was disallowed and VAR awarded a corner to Barca.
Jude Bellingham scored the decider in the 91st minute, securing Real's fourth consecutive win over the Catalan side. Second-placed Barca trail by 11 points, a deficit that will be difficult to overturn with six games remaining.
"We can't control them. These are refereeing actions. I think the team is doing very well, we competed very well, we were better than Real on their own pitch and I think we deserved the three points in every way," Xavi told reporters.
"My feeling today is one of maximum injustice. Goes without saying, everyone saw it," he added. "My feeling is that today's match was not fair."
LaLiga is the only top-five league in Europe not to use goal-line technology. After Barcelona fans criticised LaLiga for lacking the tech, chief Javier Tebas responded on X by sharing several reports of past incidents where the technology was shown to be inaccurate saying, "no comment".
Barcelona, who were knocked out of the Champions League last week, host Valencia in LaLiga on April 29.