Real Madrid, Barcelona, and Athletic Bilbao are taking legal action against La Liga over a 1.994 billion euro private equity deal that the administrators of elite Spanish soccer agreed last week, the clubs said on Wednesday.

All but five of the 42 clubs in the top two divisions signed up to the 1.994 billion euro ($2.24 billion) investment from CVC Capital Partners, the first of its kind in Europe. Four clubs, including the top-flight trio, opted out and one abstained.

The deal was "an illegal transaction that causes irreparable damage to the entire Spanish football sector and flagrantly violates the most elementary principles of Spanish sports law and the La Liga statutes," Real Madrid, Barcelona, and Athletic Bilbao said in a statement announcing legal action and published on their websites.

The agreement, dubbed "LaLiga Boost", buys CVC an 8.2% stake in a new company that will get broadcasting revenues and sponsorship rights for 50 years. It commits clubs to allocate 70% of funds for investments to new infrastructure and modernization projects. Up to 15% can be used to sign players, with the remaining 15% for reducing debt.

La Liga said it confirmed the legality of the deal. "This decision by Real Madrid CF was a foreseeable reaction, given the Club's history of head-on opposition and appeal against any strategic initiative that represents an advance and a boost for the competition and its clubs," it said in a statement.

The CVC deal looked at the risk of unraveling last week when Barcelona, Real Madrid, and Athletic Bilbao proposed an alternative proposal for JPMorgan, Bank of America, and HSBC to jointly lend 2 billion euros in exchange for a fixed annual payment of 115 million euros over 25 years, a document seen by Reuters showed.

Barcelona and Real Madrid were also among the driving forces behind a failed plan to launch a breakaway European Super League earlier this year and vowed to continue to try to set it up.