One of the publications, the French investigative portal Mediapart, said Ronaldo and his Portuguese compatriot Mourinho had benefited from a tax optimisation system developed by their agent Jorge Mendes, who owns Gestifute.
The soccer agency Gestifute has denied that clients including Portuguese star Cristiano Ronaldo and Manchester United manager Jose Mourinho are involved in any tax evasion after a media consortium reported that they had used tax havens to handle tens of millions of euros in earnings.
A group of 12 European news outlets on Friday began publishing the results of months of investigations into a vast trove of more than 18 million financial documents, obtained by the German magazine Der Spiegel and dubbed the "Football Leaks".
"Both Cristiano Ronaldo and Jose Mourinho are fully compliant with their tax obligations with the Spanish and British tax authorities," Gestifute said in a statement.
"Any insinuation or accusation made to Cristiano Ronaldo or Jose Mourinho over the commission of a tax offence will be reported to the legal authorities and prosecuted."
The European Investigative Collaborations (EIC) consortium, which includes Britain's Sunday Times, Portugal's Expresso and Spain's El Mundo, intends to release details of its findings over the next three weeks.
Reuters was unable to independently confirm the accusations.
Spanish prosecutors did not respond to requests for comment; nor did Real Madrid, Ronaldo's present and Mourinho's former club. Mourinho's new employer, Manchester United, said the allegations predated his arrival there and that it would have no comment.
One of the publications, the French investigative portal Mediapart, said Ronaldo and his Portuguese compatriot Mourinho had benefited from a tax optimisation system developed by their agent Jorge Mendes, who owns Gestifute.
Mediapart said the system Gestifute employed for its various clients, using a network of offshore accounts and companies, represented a total potential loss to tax authorities of at least 185 million euros.
In its statement, Gestifute said that "neither Cristiano Ronaldo nor Jose Mourinho have ever been involved in legal proceedings regarding the commission of a tax offense".
Image: Jose Mourinho (left) and Cristiano Ronaldo
Photograph: Gonzalo Arroyo Moreno/Getty Images