COPE have accessed a copy of the document presented by the lawyer Jacinto Vicente, in the name of an un-named assistant referee, relating to pressure reportedly being put on an official(s) to favour Real Madrid in the Clasico.
Among other things, it highlights that the former referee Muñoz de Morales would have, reportedly, been the person making the referee recommendation for the Clasico.
In the document it's explained that the supposed phone call took place in September.
Vicente writes: "In this context, in the middle of September, with two months still to go [before the Clasico], a referee said to my client he had received, and I quote, 'an instruction directly from someone inside'.
"The guidelines said that they could be the refereeing team for the Clasico -- even though it has still not been named, nor will it be until closer to the date -- between Madrid and Barcelona on November 21.
"In the case that they were designated the game, it was indicated that they must try to referee the game in a certain manner, in more certain terms, to prejudice the interests of one of the clubs, FC Barcelona."
Later, in the same document, it specificed that it's the principle referee of the officiating team who called the assistant to say "it would be more convenient if the most difficult decisions in this game are not taken by the main referee, as it generates more controversy in the media, but by my client, the assistant."
Vicente continued: "If the decisions are made by the assistant, it was considered, less controversy would be generated and it would also dilute more quickly. In addition, it was also stated that this practice has already been tested in 2014-15 and that, precisely, on that occasion the main referee was exposed and critised by the media. For that reason, it was convenient to be more subtle."
Further on in the document, Vicente also suggests it is not the first time an official has been pressured. Without revealing the identy of the victim, it could have been one of Jose Luis Gonzalez Gonzalez's assistants.
You can read the full document here (in Spanish).