United have just agreed a £5.4million deal for Corinthians defender Dodo, 17, who has yet to make a single full appearance for his club.
And Alberto said: "It is disgraceful United are allowed to rape Brazilian football.
"The big teams have the money and can take our best players. It is a big problem in Brazil. The clubs cannot keep hold of them if they are good young players because they can make much more money in other countries.
"They should change the law so at least until the age of 20 or 21 the best players are playing in Brazil and get some experience before moving to Europe."
Dodo, rated the best young defender in Brazil, is half owned by Corinthians and half by third-party investment firm Traffic Football Management.
United struck a deal last year with the company giving them first option on around 120 teenage players being groomed for European football in a Sao Paulo academy.
And just like twins Fabio and Rafael, who joined United two years ago, Dodo will not have been seen by Brazilian fans by the time he joins up with United next year.