De Telegraaf reports that the Dutch club do not want to part with the 22-year-old during the current transfer window and then raised the financial demands in talks with Manchester United from €80m to €100m.
Several important players have already left Ajax this summer, so the club see no need to part ways with the Brazilian.
Journalist Jacques Talbot, citing De Telegraaf insider Mike Verweij, writes that Antoni himself wants to move to Manchester United, but Ajax have no intention of letting him go.
The Brazilian national team player played 33 games for Ajax in all competitions last season, scoring 12 goals and providing 10 assists.