Approximately 200 home fans located in the 'ultras' section of Barca's stadium sang 'es un borracho, Cristiano es un barracho!' midway through the second half of Sunday's La Liga fixture, according to La Liga's governing body LFP.
The term 'barracho' translates to 'drunk' in English, and it is thought Barca's supporters were mocking Real Madrid star Ronaldo for holding his 30th birthday party just hours after his team's 4-0 derby defeat to city rivals Atletico Madrid on February 7.
The LFP has deemed this to be in contravention of the RFEF's Disciplinary Code, which outlaws any chant that incites "violence, racism, xenophobia and intolerance".
Therefore, the league has announced its intention to pass on a written denouncement of the chant to the federation's Anti-violence Commission on Thursday.
In a statement released on Tuesday, the LFP cited the Barca fan group 'Almogavers' as particular offenders for the "repetitive, choral and coordinated form" of the chant, but also stressed that the song was not taken on by the rest of the crowd, whose "behaviour was completely correct during the whole game".
