Reform reported Lowe to the police on 6 March over claims of threats of physical violence directed towards Yusuf.
The party also hired a lawyer to investigate allegations of workplace bullying in his office made by two female employees.
Lowe denied wrongdoing and said the claims were retaliation after he criticised Farage in an interview with the Daily Mail, describing his then-leader’s style as “messianic”.
In her report, the lawyer Jacqueline Perry KC, concluded there was “credible evidence” Lowe and his staff had mistreated two female team members in ways that “seem to amount to harassment”.
She also said Lowe had failed to “address the alleged toxic conduct” of male colleagues in the office.
Responding to her report, Lowe said the claims were “outright lies” and labelled the process “disgustingly bias”.
Reform expelled Lowe from the party, having previously suspended him.
One of the women involved has also made a formal complaint to the Parliamentary Independent Complaints and Grievance Scheme.
