UEFA has opened a disciplinary investigation into the involvement of Real Madrid, Barcelona and Juventus in the European Super League.

The three clubs are founder members of the breakaway competition and have yet to give up on the project, despite nine other teams stepping away.

Among the sanctions they could face is a two-year suspension from European competition, with UEFA claiming they will take a "take whatever action it deems appropriate".

“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, Barcelona and Juventus in connection with the so-called ‘Super League’ project. Further information regarding this matter will be made available in due course.”

Barcelona, Juventus and Madrid released a statement on Saturday hitting out at "threats" from European football's governing body, while reaffirming their commitment to the Super League.

"The founding clubs have suffered, and continue to suffer, unacceptable third-party pressures, threats, and offenses to abandon the project and therefore desist from their right and duty to provide solutions to the football ecosystem via concrete proposals and constructive dialogue," they wrote.

"It is intolerable under the rule of law and tribunals have already ruled in favour of the Super League proposal, ordering FIFA and UEFA to, either directly or through their affiliated bodies, refrain from taking any action which may hinder this initiative in any way while court proceedings are pending."

Juventus, who are in danger of missing out on Champions League qualification next season, have also been threatened by expulsion from next season's Serie A if they don't abandon the project.