TORONTO -- Ontario's premier had to shuffle a few members of her cabinet Monday as her environment minister announced his resignation, a move she insisted should not be interpreted as evidence of declining Liberal fortunes.

Environment Minister Glen Murray, who implemented Ontario's ambitious cap-and trade program aimed at reducing greenhouse gas emissions, said he is leaving his cabinet position immediately to become executive director of the Pembina Institute, an environmental think tank, effective Sept. 5. He will resign his Toronto Centre seat on Sept. 1.

Chris Ballard, who had been serving as Ontario's housing minister, was made environment minister, and former Toronto councillor Peter Milczyn was promoted to cabinet to take over at housing.

Murray's announcement came as a surprise, as he had indicated just months ago that he would run again in next year's provincial election.

But Premier Kathleen Wynne dismissed suggestions his departure is related to the Liberals' electoral prospects, which polls indicate are hurting.

"I do not see this as a vote of non-confidence," she said. "I see this as an individual having to make a decision about his life and he is a friend and I wish him well."

Murray said he has a "high degree of confidence" the Liberals will be re-elected. He just decided that he had hit his political "best before date," he said.

"I always think that when you get into politics you have to have an exit ramp, and that's either a time deadline or it's a set of circumstances where you know you've done what you can do and then it's time to get out," Murray said in an interview.

"I've been struggling for a long time about do I do another four years or do I wrap it up at this point, and I was very seriously planning to run probably up until a couple months ago, when the Pembina job came open."

He described the move to Pembina as an opportunity to dedicate the rest of his life to fighting climate change.

A former mayor of Winnipeg, Murray was first elected to the Ontario legislature in 2007 and served as minister of research and innovation and minister of training, colleges and universities under then-premier Dalton McGuinty.

He ran for the party leadership, but dropped out to support Wynne, and after she was elected premier, she gave him the portfolios of infrastructure and transportation.

Murray developed a reputation around the legislature for impassioned defences of environmental policy, a willingness to opine on the topic at length, and an eagerness to take on critics.

Wynne alluded to Murray's outspoken nature, saying she is glad as leader that her cabinet and caucus members say what they think.

"From my perspective there is no point in having a group of people who simply nod and smile when I put forward a plan or an idea," she said.

Wynne also cheered Murray's advocacy for the LGBTQ community as the country's first openly gay mayor.

"Glen's career has courageously lead by example, paving the way for people to be their true selves and become whatever they want to be," she wrote in a statement.

Wynne said she would not be calling a Toronto Centre byelection with just nine months before the start of a provincial election campaign.

"There is a significant cost associated with running byelections," she said. "We're moving into that period well within a year of a general election and historically there has been a practice when you get that close it's not necessarily responsible to call a byelection, so we won't be doing that."

Wynne also announced Monday that francophone affairs will become a standalone ministry. Marie-France Lalonde, the corrections minister, who is already responsible for the file, will become the minister of francophone affairs.

-- With files from Mia Rabson in Ottawa.