The preliminary investigation concerns a post on Facebook, where Ebba Busch (KD) commented on her infected domestic dispute.
In the post, Ebba Busch asked if a legal representative linked to the seller really represents his client's will.
Busch also wrote that the representative has previously been convicted of crimes that go far back in time.
A report of gross defamation was submitted - and a preliminary investigation is underway led by the Special Prosecutor's Office to find out if a crime has been committed that falls under public prosecution.
SVT Nyheter has been in contact with the designated legal representative, who does not want to comment on the investigation.
He instead refers to his lawyer.
According to the Riksdag, it is not relevant to limit Ebba Busch's assignment during the course of the investigation.
A member may be forced to resign if he or she is deemed unfit for the job by committing a crime, a decision made by a court.
Ebba Busch denies all allegations of alleged crimes, and the Christian Democrats' press manager announces that the party leader refers all questions about the case to lawyer Thomas Olsson.