Barcelona president Sandro Rosell today accused Real Madrid and their coach Jose Mourinho of going too far last season with their "totally unfounded accusations" against the Catalan giants.
Relations between the arch rivals plummeted during a run of four matches in just 18 days between the two Spanish giants in the Primera Division, Champions League semi-finals and Copa del Rey final.
Speaking at a press conference today, Rosell hit out at Madrid's conduct in a lengthy statement.
He said: "We feel that this season Real Madrid have gone beyond all the limits of necessary sporting rivalry, directing accusations towards our club, without any type of foundation."
Madrid boss Mourinho caused a huge controversy in his post-match press conference following April's Champions League semi-final first leg at the Bernabeu when he implied Barca receive favourable treatment from referees and claimed the Catalan club had yet to win a "clean" Champions League title under coach Pep Guardiola.
That ill-tempered encounter also saw both Spanish rivals lodge complaints against the other to UEFA afterwards, with Barca singling out Mourinho for his comments and Madrid responding by accusing the Catalan club's players of "feigning aggressions" during the clash.
Ahead of the second leg in Barcelona there were also allegations of racism against Barca midfielder Sergio Busquets towards Madrid defender Marcelo in the same game.
Rosell, whose club won the semi-final 3-1 on aggregate and went on to beat Manchester United in the final, said: "Comments by the protagonists have always served to enrich footballing debate.
"But this season a Real Madrid employee, their coach, went beyond all the limits of necessary sporting rivalry.
"He even went as far as to say that our coach should feel ashamed of some of our victories. The press conference given by the Real Madrid coach after the first leg of the Champions League semi-finals at the Bernabeu would certainly have made any sportsperson feel ashamed.
"He accused our club of having won titles thanks to some kind of national and international conspiracy, implicating in this conspiracy the good name of Unicef and the football authorities.
"We obviously defended ourselves, by presenting a formal complaint to UEFA, who finally decided to sanction him."
Mourinho was handed a five-match touchline ban by UEFA in relation to the semi-final first leg, which saw the Portuguese sent to the stands during the game prior to his post-match tirade.
Madrid have appealed against that ruling.
UEFA dismissed the allegations of racism due to "a lack of strong and convincing evidence," while European football's governing body also rejected Madrid's complaint about the supposed play-acting of Barca's players during the match.
Rosell also commented on a report on Spanish radio station Cadena COPE earlier this year regarding allegations linking Barca to doping practices.
"We defended ourselves, and went to court to deny the accusations made by Cadena COPE, who repeatedly gave the name of Real Madrid as the source and origin of the information," said Rosell.
"I can assure you that if anybody, in the name of Barcelona, had dared to make such an accusation, we would have acted firmly, denying this immediately and taking those responsible to court. We would have liked a similar response from Real Madrid, but sadly we never got one."
In concluding his statement, Rosell said: "The rivalry will continue next season, but we cannot allow the limits of fair play to be passed again.
"If the limits of fair play are passed once again, we shall be obliged to end our institutional relations, something we have absolutely no desire to do. We do not want to do that, but we are not afraid of doing it if we have to.
"A few days ago, the president of Real Madrid (Florentino Perez) said he will not stop until they win "the 10th" (European Cup title).
"We hope he tries to do that on the field of play, in a sportsmanlike fashion and returning to the methods that, we feel, many Madrid fans prefer. The president of Real Madrid has the opportunity to revive our relations, both on and off the field
"By means of this institutional statement, Barcelona wishes to put an end to this lamentable episode, which we hope will never be repeated again, for the good of football, of sport and of all of us that love it."