A longtime BC Liberal has left the ruling party to join the Conservatives, citing concerns with the party's leadership.

Abbotsford South MLA John van Dongen announced his decision in a speech in the legislature Monday.

"I can no longer carry on with my duties as a member of this government," he said in prepared remarks.

"I believe the people of B.C. deserve a government that will look in the mirror and honestly contemplate what it sees in the reflection; a government that people have trust and confidence in; a government that models true accountability for its own actions."

In an interview with CTV News, van Dongen said he has yet to discuss his decision with Premier Christy Clark.

Van Dongen has served in the legislature since 1995, holding positions including minister of agriculture and solicitor general. He resigned from the latter position in 2009 after it was revealed that he lost his driver's licence over a series of speeding tickets.

Monday's announcement makes him the only sitting BC Conservative MLA.

"I will put my time, energy and talents to serve my constituents and the party that can best provide British Columbians with a broadly-based, credible, free enterprise option," he said of his new party.

Van Dongen said that he had been hopeful that Clark's leadership would bring a sense of renewal to the Liberals and their government, but he was disappointed by the results.

"Indeed, every week constituents question government actions and issues that I am not able to defend," he said.

In particular, he pointed to concerns about the $6 million in legal fees paid out to the two former government aides who pleaded guilty in the BC Rail scandal as well as the death of a lucrative deal with Telus for naming rights to BC Place.

Van Dongen openly questioned Clark's ability during last year's leadership campaign and said he would reassess his position as a Liberal if she won. Clark was not in the legislature when van Dongen announced his resignation.

At a press conference later Monday afternoon, van Dongen questioned the Liberal party and Clark's integrity.

"I couldn't in good conscience, continue to support the premier. I didn't have sufficient confidence in the integrity, the foundation of the party to be able to continue on," he said.

Conservative leader John Cummins gave a hearty welcome to the new recruit and said the MLA's experience would be a big asset for the party.

"John van Dongen is a man of principle and integrity, and I am delighted that he has joined BC's fastest growing party," Cummins said in a release.

Liberals took a hard line on their colleague's decision and Energy Minister Rich Coleman suggested that van Dongen has been going through tough times.

"This guy's a friend of mine, and I watched him go through a period of time in his life that I think has been very difficult for him, and I've spent a lot of time with him as he's dealt with that. I think maybe that's impaired his judgment here," Coleman said.

Van Dongen's move marks a strong blow for the Liberals, which have been floundering in the polls.

The party was tied with the surging Conservatives at 21-per-cent support in a poll performed by Forum Research last week. That same survey had 47 per cent of respondents saying they'd vote for the NDP if an election was held today.

Mario Canseco, a pollster with Angus Reid Public Opinion, told CTV News that van Dongen's decision comes at a crucial time for the Conservatives, with byelections scheduled next month for Port Moody-Coquitlam and Chilliwack-Hope.

"This is big for the Conservatives," Canseco said.

"This is happening right before the byelections, which provides the BC Conservatives with an opportunity to say, ‘Even if we lose Chilliwack, we still have somebody in the legislature who will fight for you.'"