John van Dongen emerged from the party's annual general meeting saying he could not continue under the leadership of John Cummins.
"I am turning in my BC Conservative party membership," van Dongen told reporters shortly after about 70 per cent of party members who cast ballots voted against a review of Cummins' leadership.
"I could not in good conscience pretend that I could support John Cummins for a future premier. I don't believe he has the capacity to do the job."
The MLA for Abbotsford South cited the party's third-place finishes in two recent byelections as examples of Cummins inability to lead.
"I just don't think that John Cummins has the right stuff to be leader of a party, and in fact, I believe that public opinion and their assessment supports that view."
Van Dongen, who bolted from the governing Liberals to the Conservatives after Christy Clark was chosen as that party's new leader, said he will sit as an Independent in the legislature.
Earlier, the party announced that 71 per cent of about 1,000 members who cast ballots voted against a leadership review, and 29 per cent in favour.
The leadership dispute centred around the leadership style and a $4,000 a month stipend for Cummins, a former Conservative MP federally.
Cummins described the vote as procedural, and said nonetheless he was pleased with the results.
"My name wasn't on the vote. The vote was about process and whether the party thought a leadership review would be essential," he told reporters after a lengthy speech to about 200 party members who gathered at the Langley Events Centre for the annual general meeting.
"We're moving on."
Cummins did acknowledge there is some "upset" among those who were pushing for a review but said he said he didn't know what the issues are.
"I can't make heads nor tails. I'm not going to waste my time trying to. We've got an election to fight in eight months and that's what we're focusing on," he told reporters.
Cummins said no leader can expect to get 100 per cent support, and that he's satisfied with the 71 per cent vote.
"It's been tough, it hasn't been positive. There's no question about it. "
Van Dongen says he will go to the Liberal Party convention this fall, and left the door open to rejoining the party, although not under Clark's leadership.
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