Barcelona coach Ronald Koeman is demanding an investigation into the leaking of Lionel Messi's contract.

El Mundo has been heavily criticised for publishing details of Messi's current contract - including the total amount of €555m the Argentine is taking home for the length of the deal.

“It is unbelievable," blasted Koeman after victory over Athletic Bilbao. “We have known for a long time that he is the best footballer in the world and that he has done a lot for this club.

"Today he also scored a great goal from a free kick.

“Respect must be shown. There are only bad intentions behind this. With publications such as this one it is consciously looking to cause damage.

"I really do not understand that one can claim that Messi is the one who supposedly ruined Barcelona. He has been showing his qualities as a football player for years and has helped to make this club very big. If someone leaked this from the club, then that's a particularly bad thing. When you are part of the club, you must help and support the club, the coaching staff and the players.

"If someone from the club has done this… Whoever has done this cannot have a future here."