The Financial Times newspaper writes about this with reference to its own investigation. 

According to the publication, members of the organization recruited young girls mainly from rural working-class areas, promising them an education in return for joining Opus Dei.

“The women said they were forced into domestic slavery—essentially modern slavery—through a harsh system of psychological control,” the publication said.

As one of the victims told the publication, at the age of 15, the priest invited her to join the organization.

According to the woman, she worked for many years as a domestic servant for free.

At the moment, the Opus Dei organization includes about 95 thousand people around the world.