Matt Toner ran for the NDP in the Vancouver-False Creek riding two years ago and finished second to Liberal Sam Sullivan.
The high-tech entrepreneur and former naval reserve officer criticized on Tuesday the NDP's head-in-the-sand rebuilding efforts and said he became disenchanted with the party after it replaced former leader Adrian Dix without embarking on a brutally honest discussion about policies and directions.
John Horgan was acclaimed NDP Leader in May 2014. The only other official leadership candidate, Port Coquitlam New Democrat Mike Farnworth, quit the race and threw his support behind Horgan.
"You had this coronation of John Horgan without a leadership contest that asked people for new ideas," said Toner. "You just sort of had this thing, 'Well, I think we're OK. We made a change and now bring on 2017.' It's fundamentally something I just disagree with. I don't think the world works that way."
He said the NDP's grassroots is ripe with people willing to consider and test new ideas and approaches, but the party brass and its machinery are not as open to change.
"I never had any real issues with any people in the NDP," said Toner. "They are some of the best folks I've met. But I think the party itself is trying to solve the problems of the 1960s with politicians from the 1990s."
He said he was drawn to the Green party because of its approaches to environmental stewardship and economic sustainability and wants to represent it in the riding of Vancouver-Mount Pleasant.
A byelection is expected there after longtime NDP MLA Jenny Kwan was nominated to run for the federal NDP in the neighbouring Vancouver-Hastings riding. A federal election is expected to be called this fall.
The Green party has welcomed Toner and calls him a high-quality candidate.
Lone B.C. Green party MLA Andrew Weaver said in a statement that Toner represents the new breed of politician British Columbians are seeking.
"Matt will play a key role in developing the B.C. Green party vision for a diversified, sustainable 21st century economy," said Weaver.
"It would be an honour to see Matt Toner's MLA name plate on an office door in the Legislature."