London Welsh have been charged with fielding an ineligible player in a number of Aviva Premiership matches.
The club have confirmed that the charge related to scrum-half Tyson Keats, who joined the side from Aironi last year.
The club's CEO Tony Copsey said in a statement: "This is obviously a serious matter which the club has not only brought to the attention of the RFU but is also working closely with the RFU to provide full cooperation whilst the case is being prepared and ultimately heard next week.
"Due to the sensitive nature and the impending hearing the club is unable to make any further comment at this time."
The RFU will hear the Exiles' case on March 5.
The governing body has previously docked points and handed down fines to clubs who have fielded an ineligible player.
