Senate authorities have opened a sexual harassment investigation following a formal complaint lodged by a former employee of long-time Liberal Senator Colin Kenny, CBC News has learned.

Reporting by Radio-Canada's Brigitte Bureau has also uncovered that this is not the first time that Kenny has faced complaints about his behaviour towards women.

A woman who worked at a tanning salon Kenny used to own complained to police that he told her to perform oral sex or risk losing her job. Police dismissed the complaint as not credible.

Bureau has also obtained a 2001 letter sent by a North Atlantic Treaty Organization official alleging Kenny paid "persistent" and "unwelcome" attention toward two women working at the NATO Parliamentary Assembly.

It is important to note that none of these allegations have been proven in court. Kenny said he cannot comment on the complaint by his former Senate staffer because the matter is under investigation. He called all the allegations “bogus.”

Liberal Leader Justin Trudeau‛s office said Thursday that Kenny has withdrawn from the Liberal caucus while the investigation continues.

”We can confirm that Senator Kenny informed us yesterday that he was withdrawing from the Liberal caucus effective November 13th, pending the outcome of an investigation by the Senate administration,” Kate Purchase wrote in an email to CBC News.

'Sexual comments'

Pascale Brisson, a former assistant to Kenny, recently told CBC News that half her day was spent tending to his personal affairs rather than taking care of Senate business.

She also alleged Kenny sexually harassed her.

"He said sexual comments at work and also invited me over to his house for a few drinks," Brisson told Bureau.

"At that moment, I asked if it was related to work. He said he just wanted to get to know me. So, I refused the invitation."

Brisson also said Kenny asked her to wear high-heeled shoes to work and would stand with his hand on her waist when they were meeting alone in his office with the door closed.

"When we were discussing different issues, it would happen sometimes that he would put his hand around my waist or try and come closer to me to talk to me. I didn't really feel comfortable at the time with such things, so i would just take a step back and continue the conversation," Brisson said.

Brisson filed a formal sexual harassment complaint in the past few weeks.

International group complained about behaviour

In 2001, Kenny was active in the NATO Parliamentary Assembly, a working group of politicians from NATO countries.

The group wrote a letter to the head of the Canadian delegation, then-Liberal MP Carolyn Parrish.

The letter, obtained by CBC News, alleges Kenny made frequent phone calls to a female intern and female staff member.

"In both cases, the women affected by this problem have indicated ... that the attention they received was unwelcome, upsetting and made their work environment uncomfortable," wrote Simon Lunn, who was at the time the secretary general to the NATO Parliamentary Assembly.

One of the women was "considerably distressed" by the attention, Lunn said. The other said that "what began as a friendly meeting became persistent and unwelcome attention," he wrote in the letter.

Parrish says the NATO group urged her to oust Kenny from future trips to assembly functions.

"It was just general harassment. All that came to my attention was hundreds and hundreds of phone calls and requests to go out for dinner and requests to socialize," Parrish said.

Demanded sexual favours

There have been other allegations made against Kenny outside his role as a senator.

For several years, he operated two tanning salons in Ottawa. Candace Amis worked for Kenny in 2003 when she was 19.

She says one night, when the two of them were alone in the salon, Kenny demanded sexual favours.

"He wanted to see my breasts and I did not want to do it. I made it clear that I was uncomfortable," she said.

"And he communicated to me that if I didn’t take my shirt off then I wasn’t 'performing' as to be expected, to the level he wanted me to perform at my job. And so, therefore, he would have no other choice but fire me. So I took my shirt off."

Amis said Kenny then told her to take off her pants, then to perform oral sex on him.

"I was in shock. And he communicated again that, are you going to give me a blow job or you’re going to lose your job. That was it, that was all. You’re going to take your shirt off, you’re going to take your pants off, you’re going to give me a blow job and that’s it."

She says she complied because she was afraid of losing her job.

'This job meant a lot'

Amis grew up in foster homes and was an exotic dancer when she got a job at the tanning salon. She had just moved from a shelter into a rooming house, and was about to start university.

"This job meant a lot to me at the time," she said.

"I wanted to be able to ensure I could pay for [the room] without having to depend on having to do dancing," Amis said.

"I felt like [a] self-productive, functioning member of society."

Amis complained to the Ottawa police. They didn't believe her story, in part because she had lied to the police in the past.

A former employee of the senator says she now regrets not corroborating Amis's story because she knew other workers had also complained about him.

Another former employee spoke to CBC News about an encounter with Kenny. She says he was waiting for her one morning when she arrived to open the salon.

"He was naked from the waist down and I got the full frontal view of him. And when I came in, he didn't apologize," said the former employee, who requested anonymity.

Kenny wouldn't address Amis's allegations, other than to say they are "fabricated."