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UEFA have opened a disciplinary investigation against Real Madrid, Barcelona and Juventus over their part in the European Super League project, European football's governing body has announced.

The trio of clubs were among 12 founder members of the competition last month but are the only ones not to have renounced the competition and recommitted to UEFA.

A statement said: "In accordance with Article 31(4) of the UEFA Disciplinary Regulations, UEFA Ethics and Disciplinary Inspectors have today been appointed to conduct a disciplinary investigation regarding a potential violation of UEFA's legal framework by Real Madrid CF, FC Barcelona and Juventus FC in connection with the so-called 'Super League' project.

"Further information regarding this matter will be made available in due course."

The maximum punishment available to those inspectors would be a two year ban from the Champions League with UEFA president Aleksander Ceferin having been forthright and robust in his treatment of the breakaway clubs since the league was announced on April 18.

Within 48 hours its six English clubs had withdrawn with Atletico Madrid, Inter Milan and AC Milan abandoning the project soon after. Those nine teams agreed to sanctions including a five percent fine for one season of European football when they formally returned to the fold on Friday with UEFA warning that it "has reserved all rights to take whatever actions it deems appropriate against those clubs that have so far refused to renounce the so-called 'Super League'."

Madrid, Barcelona and Juventus continue to stand by their competition and on Sunday released a lengthy statement insisting that their actions were lawful, that they remain committed to the project and that they were looking for solutions to the "existential questions which threaten football". Each of the three clubs have found long-term revenue challenges to be further exacerbated the coronavirus pandemic and Madrid president Florentino Perez made no secret of the fact that the Super League offered a chance to resolve the financial issues at his club.

As such the threat of missing out on Champions League football, for which they are set to earn between $84.1million (Juventus) and $112million (Real Madrid), could prompt the three remaining rebel clubs to make amends with UEFA.