Vertonghen admitted during negotiations he felt let down by Ajax as details of his contract were leaked to the press.
"It was not easy," Vertonghen told De Telegraaf. "Maybe it's because it was my first big transfer, but the problems that arose, I had not expected. I found that I - in relation to that fifteen percent of the transfer fee - was within my rights."
He added: "The business side of Ajax I understand. I understand that the club financially wanted the most out of it. But that is now ancient history. Actually I am also satisfied that Ajax got nine million for me and through bonuses it can be up to twelve million."