A controversial deal struck by the Park Geun-hye administration with Japan on the indirect compensation of Korean wartime sex slaves was wrapped up in secret concessions from Seoul, a report published Wednesday shows.

The report written by a Foreign Ministry task force says that the deal signed in December 2015 came with an "undisclosed agreement" about Seoul's promise not to support statutes and other memorials honoring the victims.

It also promised Tokyo not to use the term "sex slaves" for the women but call them "Japanese military comfort women victims," which obscures the nature of their ordeal.

The Park government also failed to immediately inform the victims that the deal was "final" and "irreversible" when it tried to persuade them to accept it, according to the report.

The report puts the new government in a bind, with Tokyo warning that relations will become "unmanageable" if Seoul were to seek a change in the deal.