Five allegations by a Westminster staffer were made in October 2021 after a complaint made to then prime minister Theresa May in 2017 went unresolved, the IEP said.
The complaints included four allegations of bullying, detailing that Mr Bone "verbally belittled, ridiculed, abused and humiliated" his employee and "repeatedly physically struck and threw things" at him.
The report said Mr Bone also imposed an "unwanted and humiliating ritual" on him by forcing him to sit with his hands in his lap when he was unhappy with his work and that he ostracised his staff member following an incident on a work trip to Madrid.