Saracens are reportedly now at risk of being thrown out of the Champions Cup this season.
The club, who have already been officially been relegated from the Premiership, admitted they may have fielded an ineligible player in their recent pool stage victory over Racing 92.
The EPCR said it was told by Saracens that prop Titi Lamositele may have been ineligible.
An independent disciplinary committee will hold a hearing at 18:00 GMT on Friday.
A statement from the EPCR said that Lamositele may have been ineligible when he came on as a replacement in the 60th minute “due to an inadvertent administrative error on behalf of the club”.
The 24-year-old was eligible when Saracens’ matchday squad was announced, but his work permit had expired before the game on 19 January.
The full statement read: “Following an investigation, EPCR has decided to bring a misconduct complaint against Saracens arising from the club’s Heineken Champions Cup, Round 6 match against Racing 92 on Sunday, 19 January.
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“EPCR was informed by Saracens earlier this week that their player, Titi Lamositele, who was named in the match day squad for the fixture at Allianz Park and who came on to the field of play as a replacement in the 60th minute, may have been ineligible due an inadvertent administrative error on behalf of the club.
“Lamositele was eligible at the time the Saracens match day squad was announced, however, the club has indicated to EPCR that the player’s work permit expired on Saturday, 18 January, the day before the fixture against Racing 92, and this may have constituted a breach of the Disciplinary Rules of the 2019/20 EPCR Participation Agreement.
“An independent Disciplinary Committee consisting of Roger Morris (Wales), Chair, Pamela Woodman (Scotland) and Jean-Noel Couraud (France) has been appointed to hear the misconduct complaint in London this evening (Friday, 7 February) at 18.00 local time.
“EPCR will be making no further comment until the decision of the independent Disciplinary Committee has been communicated.”