MANCHESTER, England (REUTERS) - The Spanish soccer league's organising body La Liga is ready to turn to the European Union if Uefa does not enforce its Financial Fair Play (FFP) rules against Manchester City and Paris St Germain, a spokesman told Reuters on Tuesday (Nov 6).

"Football Leaks" documents, showing the two clubs had inflated sponsorship revenues to meet the requirements, were obtained by the German publication Der Spiegel and reviewed by Reuters in partnership with European Investigative Collaborations, a consortium of international media.

The FFP rules are intended, among other things, to prevent clubs receiving unlimited amounts of money through inflated sponsorship deals with organisations related to the owners. According to the documents, Uefa's regulatory body accepted Manchester City and Paris St Germain receiving income from key sponsors related to the club owners that was far in excess of the market value estimated by independent experts hired by Uefa.

The cache, which spans much of the past 10 years, includes previously undisclosed details of Uefa's investigation of the two clubs' financial affairs and the settlement terms relating to the FFP rules of European soccer's ruling body.

"The Football Leaks documents appear to confirm what we have been saying for years," La Liga spokesman Joris Evers told Reuters, saying PSG and Manchester City should be sanctioned.

He said that his organisation did not have "full confidence" that Uefa would enforce FFP rules, adding: "Should Uefa fail to act, we will do what we have said before: launch a complaint with EU competition authorities."

He declined to comment on whether the case would be brought against Uefa or against the clubs.

Borja Garcia, a senior lecturer in sport policy at Loughborough University and an expert in EU sport policy and law, said it was difficult to see how La Liga could launch a challenge on competition grounds against Uefa over FFP rules.

"Previous challenges to FFP have not been successful and it is not clear how La Liga would argue that competition law has been broken," Garcia said.

Premier League champions Manchester City and Ligue 1 title holders Paris St Germain did not immediately respond to a request for comment on the La Liga statement.

City issued a statement last week saying: "We will not be providing any comment on out of context materials purported to have been hacked or stolen from City Football Group and Manchester City personnel and associated people. The attempt to damage the Club's reputation is organised and clear."

PSG issued a statement on Friday stating: "Paris Saint-Germain has always acted in full compliance with the laws and regulations enacted by sports institutions," adding that it firmly denies the allegations.

Under Uefa's FFP rules, clubs must be transparent about revenues and broadly balance them against expenditure. The rules are designed to encourage clubs to live within their means and prevent the sport's richest owners from crushing their rivals.

The European Commission was not immediately available to comment.

Uefa referred Reuters to a statement issued on Friday when it said: "We cannot comment on specific cases due to confidentiality obligations which Uefa must respect."

La Liga president Javier Tebas has long spoken out against the behaviour of Manchester City and PSG.

Evers said La Liga will wait to see how Uefa responds to the revelations before making any decisions.