Sean Kilpatrick/CP Public Safety Minister Ralph Goodale appears as a witness at a national security and defence Senate committee in Ottawa on May 30, 2016.

Ralph Goodale's appearance before the standing committee on public safety and national security was testy at points, including when Tory MPs Dave Van Kesteren and Kellie Leitch pushed him on Bill C-45, the Cannabis Act.

Canada's public safety minister made it clear to Conservatives Thursday that he has no trouble squaring his duties to protect citizens with the Liberal government's push to legalize marijuana.

Van Kesteren read a Health Canada report warning that pot use can impair concentration and decision-making, affect one's ability to drive, and in some cases cause paranoia and hallucinations. The document also warns the drug shouldn't be used by those under the age of 25.

C-45 sets the minimum age to buy and consume pot at 18, yet allows provinces to raise the limit higher. Ontario's pot plan, for instance, sets the age at 19.

"So, my question sir is: the minister in charge of our public safety and national security, how can you stand by and allow C-45 to be passed?" Van Kesteren asked.

Goodale was frank in his response, saying the Liberal bill will give Canada a "better chance" to deal with the issues he flagged.

Tory MP: 'I can't believe this'

"The existing law has failed," Goodale said. "The existing law has resulted in a situation where Canadian young people are the heaviest users of marijuana in the western world."

"You think this is going to slow down that usage?" Van Kesteren interjected.

"It has a better chance than the existing law," Goodale replied.

"I can't believe this," the Tory MP said.

A UNICEF report published in 2013 found that Canadian teens smoke the most marijuana in the western world.

While Goodale suggested it made little sense to spend $2 billion a year trying to enforce a law that doesn't work, Van Kesteren noted some police officials are advising the government to pump the brakes.

Goodale maintained the bill is better for public safety than the prohibition touted by the previous Conservative government.

The existing law has failed. The existing law has resulted in a situation where Canadian young people are the heaviest users of marijuana in the Western world.Ralph Goodale

"It has a greater likelihood to be successful than the law you endorsed which has failed," Goodale said, pointing his finger.

Leitch noted the Canadian Medical Association urged the legal age for pot use be set at 21 and charged that C-45 will make it easier for kids to possess the drug.

"Your law is very clear and you can tell me I'm wrong, but my understanding is that individuals 12 to 21 will be allowed to possess," she said.

Goodale noted that the legal age is 18, but provinces have the authority to change that where appropriate.

"The federal law is not changing the age of majority," he said.

"No, it's changing the age of possession," Leitch replied before her time was up.

She's likely getting at how the Liberal legalization plan will, if passed, exempt young people between the ages of 12-17 from facing criminal prosecution for possessing up to five grams of pot. Children who possess or distribute more than five grams would face punishment under the Youth Criminal Justice Act instead.

Justice Minister Jody Wilson-Raybould has said the provision was included because Liberals did not "want to expose young people to the criminal justice system for possessing what amounts to very small amounts of marijuana." Yet, in debate last May, Tory MP Marilyn Gladu expressed concerns kids could become "drug mules."

Watch the exchange: