Len Webber, a Tory backbencher in Alberta, has announced he is leaving Premier Alison Redford's caucus.
Webber told reporters in Calgary that Redford is a bully and he can't work with her.
"I have worked with some many great premiers in my time," told reporters Thursday, according to the Calgary Sun.
"Now the last two years under the leadership of Alison Redford I can no longer stay with the party, I can no longer sit as a government member, I cannot return to work and sit on the same side as long as Alison Redford is sitting at the helm.
"She is basically, she is really not a nice lady and I cannot work for an individual who treats people poorly , who treats our tax paying dollars poorly," the 53-year-old MLA continued.
Webber told Calgary talk radio station CHQR Thursday he had been talking privately with his colleagues for more than a year about Redford's poor leadership, knowing her office would eventually get wind of it.
"It led to a confrontation where basically I told her the truth of how I felt about her and she basically threw me out of her office," he said.
Redford has been facing a backlash from a $45,000 trip to South Africa for Nelson Mandela's funeral.
On Wednesday, after weeks of trying to weather the controversy, she said she had repaid the money.
However, Webber told the Calgary Herald the premier's announcement was "to little, too late."
“It doesn’t mean anything at all, and I don’t think she should be the person who leads the government. We need to find someone else to replace her.”
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The Edmonton Journal is reporting as many as 20 Tory MLAs had threatened to leave the party if Redford did not pay back the travel costs.
Alberta's deputy premier says the governing Tory caucus is united behind Redford.
Dave Hancock says Webber is just a "sad man," who never got over being relegated to the backbenches when Redford took over.
Hancock dismissed Webber's suggestion that Redford is a bully, saying there are a lot of strong personalities in caucus.
Labour minister Thomas Lukaszuk told the Journal Redford will have to face caucus members as a jury of peers, but would not confirm whether he supports the premier.
“I’m sure every caucus member will reflect on (Webber’s) decision, but we all have to make our individual decisions. We are all working from different subsets of fact, and that was right for him," he said.
Webber told Global News he had witnessed Redford throwing temper tantrums in fits of rage and he was tired of being treated with disrespect.
“People basically are, I believe, afraid to speak up and talk… and I can’t do that any longer,” he said.
Webber was first elected in 2004 and served in cabinet under Ed Stelmach. He has confirmed he will now sit as an Independent.
With files from the Canadian Press