In an election that has seen contenders for prime minister spar over Canada's weed laws, the official leader of the opposition expanded on his promise to decriminalize marijuana by saying that legalization is inevitable.

"I am going to start by immediately doing something that I know I can and will do overnight, which is to make sure that nobody ever has to face a charge for personal use or possession of marijuana," Mulcair said Tuesday at a town hall event in Toronto hosted by VICE Canada. "And of course we are on a track to full legalization, but it is more complicated than snapping your fingers."

Mulcair, whose left-leaning NDP party is currently third in the polls, cited legal weed regimes in Colorado and Oregon as evidence that full legalization is "the way for the future," but it won't happen in Canada right away.

"We're not going to have weed being sold at the LCBO [a government-run alcohol retailer] tomorrow morning," added Mulcair. "Making sure that nobody gets arrested for personal use. That can happen."

When Mulcair was asked whether he would decriminalize supply of marijuana, he reiterated the "need to make sure that people understand that we're going to take our time to do it. But it's going to get done"

Marijuana policy in Canada has come up frequently during the election campaign, with Mulcair and Liberal leader Justin Trudeau slamming Prime Minister Stephen Harper for his stance against legalizing weed and keeping the current criminal laws against it in place.

At a campaign stop last month, Harper warned against legalization arguing that "when you go down that route, marijuana becomes more readily available to children, more people become addicted to it, and the health outcomes become worse...I think it's actually a tragedy."

Last week, health experts criticized Harper for saying that weed is "infinitely worse" than tobacco, a claim they say isn't supported by science. The Canadian Medical Association Journal published an editorial by addiction specialists last month that argued prohibition of marijuana creates more harm than good.

Trudeau says that his party would move to legalize marijuana "right away" if elected, although he has admitted he doesn't yet know how at what rate the drug would be taxed, or when exactly it would be legalized.

The NDP leader also addressed the issue of rampant boil water advisories across First Nation reserves. It's an issue that VICE News asked Mulcair's political rival Liberal leader Justin Trudeau at another town hall on October 5. Trudeau promised to solve the issue within five years if elected.

Mulcair said he would put infrastructure in place to end boil water advisories within "two mandates," or seven to eight years — a plan he called "realistic."

"We have $500 million on the table to get this question of water right," Mulcair said. "There are 118 boil water advisories on right now in Canada … It's unbelievable that in the country in the world with the greatest quantity of fresh, renewable water, our first peoples still don't have access to clean drinking water. We're going to fix it. We're going to get it done."

VICE News managing editor Natalie Alcoba countered that he had promised $375 million over four years toward infrastructure on reserves, but that a report by Aboriginal Affairs had said in 2011 that $1.2 billion dollars is needed right away to bring reserves up to standard. "So how is your plan actually adequate?" she asked.

"What we're doing is we're starting with that, but that's the way you do government programs, you have to get them going and you have to ramp them up. What we're talking about is the money available in a first mandate, and we'd make sure we got rid of boil water advisories in that first mandate, but the structure is going to take a few more years that that. We're trying to reverse decades of neglect by successive Liberal and Conservative governments. But we are going to get it done because it's a top priority."

Pressed further for a timeline, Mulcair said it would take a maximum of seven to eight years for all First Nations to have access to clean water. "We'd have a lot of it done by the end of our first mandate, we'd have a target to get it done absolutely across the country by the end of a second mandate, that would be realistic," he said.

Both Mulcair and Trudeau have promised to reinstate a "nation-to-nation" relationship with First Nations in Canada.

_Watch the VICE Canada town hall with Thomas Mulcair here: _

The VICE News panel also asked Mulcair how he would reconcile concerns about pipelines and the environment with a commitment to keep jobs and the economy on track. The NDP leader called it a "false choice" put forward by Prime Minister Stephen Harper.

He promised to bring back the Climate Change Accountability Act and he also added to a previous promise to reform the National Energy Board, Canada's energy regulator, saying an NDP government would "bring in a system of environmental assessment that would include climate change and greenhouse gases" for every project the government considers.

That's a similar idea to the process US President Barack Obama used to make a decision on the controversial Keystone XL pipeline. He set a test that asked whether the pipeline would "significantly exacerbate the problem of carbon pollution." The president later vetoed the project.

In a nod to the NDP's orange campaign signs proclaiming "stop Harper" the leader said he would end the Prime Minister's nine-year reign.

"I'll do whatever I have to do to make sure that Stephen Harper never serves another day as Prime Minister of Canada after October 19," he said, prompting applause and cheers from the urban Millennial audience.