They says his buy-out clause is not within the spirit of the game...
FIFPro have sent a letter to the European Commission and to FIFA denouncing the new deal, which they say exceeds the time allowed for contracts under FIFA regulations.
"According to rules adopted in 2001 at the Commission, the duration of a contract should be between one and five years. Messi's new contract with Barcelona is until 2016," said Philippe Piat, president of FIFPro's European Division, as quoted by Marca.
Messi's new deal also includes an increase in the buy-out clause, from €150 million to €250 million, which has also been heavily criticised by the players' group.
"It does not conform with the spirit of the texts of FIFA," Piat said before adding that he has yet to receive a response to his letter from football's governing body or the European Commission.
Paul Madden, Goal.com