Florentino Pérez, the Real Madrid president, has taken the unusual step of speaking out publicly to deny a story which claimed the club's captains Sergio Ramos and Iker Casillas presented him with an ultimatum: if José Mourinho stays, we go.

On the day when Madrid learnt that Casillas is almost certain to miss the Champions League matches against Manchester United due to a broken finger, Pérez refused to answer questions on Mourinho's future but described the report in the newspaper Marca as "absolutely false". Marca defended its story, published yesterday, insisting: "We report what has happened."

Casillas has fractured the first metacarpus in his left hand following a clash with his team-mate Alvaro Arbeloa. He will undergo surgery on Friday. Although no formal prognosis has been offered he is expected to be out of action for up to two months, meaning that he would not be available to face United. Antonio Adán will replace him but Madrid are also looking at goalkeepers in the transfer window. "I feel truly sorry," Pérez said of Casillas's injury. Yet it was the front page of Marca that dominated the day. The paper said that during a meal with Pérez and Madrid's director-general, José Angel Sánchez, Casillas and Ramos conveyed the message on behalf of a number of players in the squad. The headline on the paper's cover read: "In June, either Mourinho or us." Casillas and Ramos had eaten with the president and director-general as they do at around this time every year in order to reach an agreement on the players' bonuses for titles won.

The response from Madrid was immediate: a press conference called for 1pm, sparking speculation. Some wondered ifMourinho was about to be sacked. Instead, he was defended. Pérez, who did not name the newspaper once, appeared angry and was direct in confronting the story, accusing some in the media of seeking to destabilise the club.

Marca's editor, Oscar Campillo, later said: "We do not seek to destabilise Real Madrid, quite the opposite. Seventy-five years' history show that Marca has always been close to Madrid. We did not say that it was an ultimatum. What we said was that some players have been disconcerted by Mourinho's behaviour and that the captains told the president that if he continues, some of the players will seek an exit."

Pérez does not often appear in public and some of the club's more radical supporters have recently been demanding that he acts more decisively against the media as critical coverage of Mourinho increases. There are presidential elections in the summer.

"I am breaking my rule of not talking about the day-to-day of the club in order to say that it is absolutely false," Pérez said.

"There no ultimatum nor anything or the sort. What has been said is not true. I think this is very serious and because of that seriousness I have decided to defend the club. Things [like this] have happened numerous times. This is the last time.

"I understand that someone may have as their objective to force someone [Mourinho] out of the club. We have just reached the semi-final of the Copa del Rey and it seems like someone does not like that. It is the unity of all the members and supporters of this club that has made it the best club in the world and we, and only we, will decide the future of our club."

He added: "There were four of us [at the meal]. Myself and the director-general, who is here. The other two have names and faces. It's not hard to speak to them to check the story. Why has no one called us? If they had called us to check it we would have said it was false. It seems that publishing the story was more important than it being true. I know what I am saying is hard but an ethical line has been crossed."Pérezaccepted questions but refused to talk about anything that was not on this specific issue, batting away e nquiries about Mourinho's future. "I have come here solely to deny a story that is false and seeks only to destabilise an institution that is over 100 years old and is the most prestigious in the world," he said. "If they want to destabilise the club, they will find me standing before them."