LaLiga last week secured a €2.7billion deal with CVC to boost Spanish clubs amid the coronavirus pandemic, with 90 per cent of the investment earmarked for their use.
However, CVC will have a 10 percent stake in a new business, which is being formed with a focus on the league's commercial ventures.
It insisted the agreement does not cover league management or broadcast rights, but Madrid and rivals Barcelona both announced their opposition to the deal, claiming audiovisual rights would be affected and they had not been properly consulted.
Madrid are now going a step further, with a rumored legal challenge confirmed in a club statement.
"The board of directors of Real Madrid, meeting today at 11:00 am, has unanimously agreed to carry out both civil and criminal legal actions against the president of LaLiga, Mr Javier Tebas Medrano, against Mr Javier de Jaime Guijarro, responsible for the CVC fund, and against the CVC Capital Partners fund itself," it said.
"Likewise, the board of directors has also decided to carry out the legal actions of all kinds that are understood to be appropriate to cancel and cancel the possible agreements adopted by the assembly of LaLiga, to be held on August 12, 2021, regarding the agreement between LaLiga and the CVC
Tebas was quick to respond on Twitter, taking aim at Madrid president Florentino Perez.
"The threatening methods that FP [Perez] has been using in private for years is now being transferred to the public," he wrote.
"Clubs and institutions have been supporting their threats for years.
"Since 2015 against the centralised sale, the constant challenges of agreements, the Super League…
"Real Madrid deserves more."
Playing behind closed doors last season, Madrid have been heavily impacted by the pandemic but have worked to limit the damage.
In their accounts last month, Madrid revealed they lost "close to €300million" in revenue, although Los Blancos reported a post-tax profit of €874,000 for 2020-21.
With "intense spending saving measures in all areas", Madrid did not make a single signing last term while moving a number of high earners off their books.
This year, they recruited David Alaba on a free transfer but saw Sergio Ramos depart and have agreed a deal to sell Raphael Varane to Manchester United.
Madrid and Barca have also continued to pursue a lucrative European Super League, as two of only three clubs – along with Juventus – still committed to the project that collapsed earlier this year.