Koeman blames Laporta and Barca management for Frenkie de Jong being forced out of the Euros due to an ankle injury.
De Jong suffered the setback in March, but still hasn't fully recovered and Koeman has since chosen to omit him from his final squad.
The former Barca captain and coach snapped: "We have concluded that even in the next three weeks De Jong will not be fully recovered.
"You have a history with this injury. His club took a risk before and now we have to pay the price."
Koeman continued: "He has not played any game nor have we seen it in the most positive way than it could be. Tests have shown that he is not yet in condition. You realize that he is not one hundred percent and that he is not in a position to play at the highest level for the next three weeks.
"You can keep him here, but it doesn't make much sense."