In an about-face, the federal government is considering a change to the Criminal Code to ban the practice of conversion therapy across the country.

In March this year, the Liberal government rejected a petition with more than 18,000 signatures calling for a national ban. It said that, "conversion therapies are immoral, painful, and do not reflect the values of our government or those of Canadians," but added that it felt conversion therapy was largely a provincial and territorial issue.

However, according to a letter signed by two Liberal cabinet ministers and an Alberta MP, and sent to the provinces in June , the federal government is now looking at ways to reform the Criminal Code in order to "combat conversion therapy."

News of the possible national ban comes as St. Albert, Alta., has become the second Canadian city after Vancouver to make it illegal for businesses to offer conversion therapy.

Other regions are also considering whether to follow suit.

WATCH: The National's story about St. Albert's conversion therapy ban

Alberta's United Conservative government says it does not condone conversion therapy. In fact, only a handful of provinces have banned it outright. But the frustration that Alberta hasn't done so has prompted one Alberta city to take its own stand. 2:10

What is it?

Conversion therapy is a practice that aims to change an individual's sexual orientation to heterosexual or gender identity to cisgender, which means identifying with the sex assigned to them at birth.

It employs various approaches, from talk therapy and medication, to aversion therapy that attempts to condition a person's behaviour by causing them discomfort through things like electric shocks when they're exposed to specific stimuli.

It is believed conversion therapy has existed for more than a century, with German psychiatrist Albert von Schrenck-Notzing being one of the first to use the practice on patients.

Peter Gajdics, author of the book The Inheritance of Shame, spent six years in conversion therapy with a licensed psychiatrist in Victoria, B.C. At first, he says the psychiatrist prescribed several antidepressants and a sedative so that Gajdics' "innate heterosexuality would resurface."

When that didn't happen, Gajdics says his psychiatrist began using aversion therapy.

"It's not so much that I wanted to kill myself as I thought I was already dead," says Gajdics, describing how he felt after he stopped seeing his psychiatrist.

WATCH: The National's video of Dr. Kristopher Wells explaining conversion therapy

Dr. Kristopher Wells is one of the driving forces behind the campaign to ban conversion therapy in Canada. He is the Canada Research Chair for the Public Understanding of Sexual & Gender Minority Youth and describes the dangers of the controversial therapy. 1:36

Where is conversion therapy offered in Canada?

These days, it's uncommon to find medical professionals offering conversion therapy to patients.

"You won't be able to walk into a licensed counsellor's office and ask them to engage in this practice, because it would be deemed to be unethical and unprofessional," says Dr. Kristopher Wells, Canada Research Chair for the Public Understanding of Sexual And Gender Minority Youth.

As a result, Wells warns, the practice has gone underground in faith-based communities, "which makes it harder to detect, but also more dangerous."

WATCH: The National's video of Matt Ashcroft and Peter Gajdics talking about the toll conversion therapy took on them

Those who've experienced conversion therapy often describe it as difficult and painful. The National reached out to two Canadians who have gone through it and they agreed to share their stories. 3:44

Does conversion therapy work?

The science says no.

Researchers at Cornell University looked at 47 peer-reviewed studies from 1992 through 2015 about the effects of conversion therapy. They found only 13 studies made an empirical determination about whether conversion therapy works.

Of the 13 studies, 12 concluded conversion therapy is ineffective and/or harmful.

The lone study that suggested conversion therapy could be successful had notable limitations, as it was entirely based on self-reporting, according to researchers.

"[Conversion therapy] can lead to depression, self-loathing … self-harming behaviours such as cutting or drug and alcohol abuse … all the way up to people taking their own lives," Wells says.

The World Health Organization issued a statement in 2012 saying this type of therapy poses a "severe threat to the health and human rights of the affected persons."

The Canadian Psychological Association, which represents psychologists, warned in a 2015 statement that, "Conversion or reparative therapy can result in negative outcomes, such as distress, anxiety, depression, negative self-image, a feeling of personal failure, difficulty sustaining relationships, and sexual dysfunction."

The CPA added that it " opposes any therapy with the goal of repairing or converting an individual's sexual orientation , regardless of age," including conversion therapy.

What are governments doing about it?

"The provincial, territorial, municipal and federal governments all have roles to play to protect Canadians from the harms associated with the practice," reads a letter sent by the federal government to the provinces last month.

The Liberal government says it plans to examine the issue with an eye to a Criminal Code ban.

Several provinces have already enacted laws to restrict conversion therapy:

Ontario has made the practice illegal for minors by initiating an outright ban.

has made the practice illegal for minors by initiating an outright ban. Manitoba has outlawed health professionals from offering conversion therapy.

has outlawed health professionals from offering conversion therapy. Nova Scotia has made it illegal for health professionals to provide conversion therapy for minors.

However, the only two jurisdictions with a complete ban on conversion therapy are Vancouver and St. Albert, Alta .

"We need to keep making sure that we're making youth safe," says St. Albert City Councillor Natalie Joly, who brought forth the motion to ban conversion therapy to council in May.

"If it means that one kid feels safe, then that risk is absolutely worth it."