The agent of Pape Gueye has questioned Watford's pre-contract with the Le Havre midfielder.
On Tuesday evening the club revealed via their website that the player had signed an agreement and would join them this summer. His deal with Le Havre expires in June.
But he player's lawyer Pierre-Henri Bovis has released a statement, declaring: "My client Pape Gueye alerted me to the particularly strange conditions under which his former agent made him sign an employment contract with Watford FC in January 2020.
"At this stage I express the most express reservations about the validity of this work contract which could have been concluded in an abusive manner, to the detriment of the interests of the player and his current club, HAC.
"As part of my mandate, I approached Havre AC and Watford to know the position of each, with regard to this situation of very great legal insecurity.
"We reserve the right, at the end of this conciliation phase, to carry out all of the contentious procedures which may prove necessary."