(CNN) -- A court's investigation into alleged financial irregularities by football club Barcelona in its purchase of Brazilian superstar Neymar should be expanded to include tax evasion by the club, a Spanish prosecutor argued Wednesday.
Prosecutor Jose Perals formally asked a judge, who is already investigating a former Barcelona president in the case, to expand the preliminary investigation, according to a copy of his writ viewed by CNN.
The prosecutor alleges that the club avoided paying 9 million euros (more than $12 million) in taxes on Neymar's signing and transfer, corresponding to contracts signed in 2011 and 2013, through a series of financial maneuvers.
Neymar joined Barcelona in June 2013, with his father -- who doubles as his agent -- having entered into an initial contract with the Spanish giants in late 2011.
In a statement on the club website, Barcelona said its "dealings with respect to this operation, and in light of all information available, was at all times in line with the relevant legal legislation."
Barca said its lawyers will appear in court "within the next few days in order to defend its interests and rights."
"We express our total willingness to collaborate with the justice authorities in this matter, as we have done since the issue arose," it added.
But Barcelona's former president, Sandro Rosell, who resigned last month after a judge agreed to investigate a lawsuit against him for irregularities in the Neymar deal, has already denied any wrongdoing.
Judge Pablo Ruz opened the investigation last month after a legal complaint from one of the members of this fan-owned club.
The request to expand the investigation came Wednesday in a eight-page writ from the prosecutor, who alleges that he's "become aware of a series of economic transactions by the club, and in favor of various companies, related to the signing of Neymar da Silva Santos Jr., based at times on simulated contracts."
It may take several days for Ruz to consider the prosecutor's request at Spain's National Court in Madrid, said a court spokesman, who by custom is not identified.
The investigation originally came after season-ticket holder Jordi Cases complained that the amount paid to bring Neymar from Brazilian club Santos was more than the reported fee of 57.1 million euros.
A day after Rosell resigned, the club released figures that showed that Barca actually paid 86.2 million euros for Neymar.
Cases' lawyer, Felipe Izquierdo, earlier told CNN that other Barcelona executives, still working at the club after Rosell's resignation, also allegedly signed some of the contracts that brought Neymar to the club.
Barcelona has confirmed to CNN that one of those signatories was former club VP, and now President, Josep Maria Bartomeu.
-- Piers Edwards and Chris Murphy contributed to this report.