Barcelona were left furious with the actions of linesman Raul Cabaero Martnez after victory over Atletico Madrid.
Barca won 1-0, though were left frustrated after a penalty appeal against Mario Hermoso's apparent foul on matchwinner Joao Felix was waved away.
Afterwards, Marca says Cabaero Martnez was spotted outside the Barca locker room, with accusations he was 'listening in' for the players' reaction to the match officials' performance.
One Barca rep spotted Cabaero Martnez and confronted the linesman, telling him to leave the Barca area.
The confrontation was later confirmed in the match report of ref Jose Maria Martinez Sanchez. He wrote: "Once the match is over and in the locker room tunnel, a person identified by the local club as Mr. Eduard Polo, head of the coaching staff press, addressed assistant 1, defiantly, in the following terms: 'You, what are you doing here?', without any further incidents to report."