The allegations in the investigation report remain unproven and none of the staffers who took part, nor any whose stories are included in the report, wanted to file a formal complaint against Sen. Don Meredith.
A Senate source with knowledge of the report, speaking on condition of anonymity because no public statements had been authorized, said the majority of the allegations against Meredith describe him as being a bully, rude and unprofessional towards his staff.
There are also allegations of psychological harassment and sometimes making irrational demands of his staff, the source said.
The executive members of the Senate's internal economy committee decided to refer the report to the Senate ethics officer, who is already conducting a preliminary investigation into Meredith on an unrelated matter.
More details of the report are expected to be made public on Thursday.
Depending on the outcome of the latest ethics review, Meredith could face penalties ranging from a forced public apology on the floor of the Senate — which is the punishment for former Conservative Pierre Hugues Boisvenu when he was found last year to have violated the Senate's ethics code — to suspension without pay.
Meredith did not immediately respond to a request for comment from The Canadian Press on Wednesday night.
The Senate first ordered the investigation into Meredith's office in February after top senators, including former Speaker Pierre Claude Nolin, witnessed what they felt was a troubling turnover of staff in Meredith's office.
The six staffers who left Meredith's office in the last four years and spoke with investigators are not identified in the report and only took part on the condition that their names be protected.
Two more staffers who left Meredith's office in the last four years declined to take part, but had their stories told second-hand to investigators from the six staffers who did speak, the source said.
Meredith is already under investigation by the Senate's ethics officer after published allegations last month that he had a sexual relationship with a 16-year-old girl.
The Toronto-area senator appointed by Prime Minister Stephen Harper left the Conservative caucus after the allegations were made in a Toronto Star story.
He has since faced calls for his resignation from senators of both stripes. Through a lawyer retained after the Star story was published, Meredith stated he fully intends to respect the internal procedures of the Senate.
Two years prior to being named to the Senate, Meredith ran unsuccessfully for the Conservatives in a 2008 byelection in the riding of Toronto Centre.
His time in the upper chamber has not been without controversy.
In 2012, Meredith landed in trouble with members of his own caucus for appearing at a Persian cultural event at Ottawa City Hall co-organized by the Iranian embassy. The Prime Minister's Office distanced itself from Meredith after the event, saying Meredith wasn't there representing the government, which has taken a hard line against Iran.
Last year, Meredith repaid the Senate for a trip he and his wife took to the National Prayer Breakfast in Washington, D.C. The annual event draws some 3,000 politicians and diplomats, including the U.S. president.
Meredith, however, didn't have any spending problems reported in the auditor general's June report into Senate spending.
Meredith also landed in hot water for referring to himself as "Dr. Don Meredith" in press releases, despite the fact his doctorate came from a institution that didn't have degree-granting powers.