A majority of 37 out of 42 clubs in Spain's top two tiers voted in favour of the investment agreement, which is worth €2.1billion.

The deal involves LaLiga giving up a percentage of revenue generated from TV rights over the next 50 years, with clubs provided a more immediate financial boost.

Barca, Madrid and Athletic have been embroiled in a war of words with LaLiga president Javier Tebas in recent weeks after describing the CVC deal as potentially "ruinous" for Spanish football.

Barca president Joan Laporta previously described the deal as like "mortgaging the club's rights over the next half-century".

In a joint statement, the clubs confirmed: "Athletic Club, FC Barcelona and Real Madrid report that they have taken legal action in response to the agreements adopted by the LaLiga Assembly in relation to the so-called Impulse Project that LaLiga intends to undertake with the CVC venture capital fund, as it is an illegal transaction that causes irreparable damage to the Spanish football sector as a whole and flagrantly violates the most elementary principles of Spanish sports law and the LaLiga statutes."

Speaking after the deal had been ratified last Saturday (AEDT), Tebas said: "We are facing a new milestone in the history of LaLiga and the clubs.

"We are proud to have reached this agreement with CVC, a project that will allow us to continue the transformation towards a global digital entertainment company, strengthening the competition and transforming the experience of the fans. 

"Despite all the obstacles that we have encountered along the way, we have carried out this project, which will be a before and after for LaLiga clubs, who will be able to improve their infrastructures, develop their brand internationally and take giant steps to continue strengthening sport and football around the world."