Sporting Lisbon are to complain to FIFA after three of their development squad players trained with Chelsea, the club said on Wednesday.
Teenagers Adrien Silva, Fabio Ferreira and Ricardo Fernandes worked out at Chelsea without authorisation from Sporting, the Portuguese club said in a statement.
A response from Chelsea to Sporting's complaints showed the English Premier League leaders wanted to recruit the players without following FIFA rules, the Lisbon club said.
"Sporting will appeal to FIFA, with the knowledge of (European soccer body) UEFA, for disciplinary action to be taken against Chelsea FC," the statement said.
"Sporting believes that FIFA will know how to protect those who, following its own recommendations, invest in and promote football development at high cost, as in this case."
Chelsea coach Jose Mourinho took over at the London side in June after winning the Champions League with Porto.
A Chelsea club spokesman was not immediately available for comment.
