A Catholic leader in Canada has warned that the upcoming legislation to legalise assisted suicide and euthanasia will "threaten the vulnerable and the conscience of those who oppose it."

Archbishop of Toronto, Cardinal Thomas Collins, also cautioned that legalising assisted suicide will "hide killing with euphemisms," the Catholic News Agency (CNA) reports.

On Thursday, Canada took a significant step towards allowing dying people to seek medical help to end their lives by passing a bill legalising doctor-assisted suicide and euthanasia under the federal criminal code.

Some Canadians have expressed reservations based on deeply held religious beliefs, but recent polling shows an overwhelming majority — 85 percent—support the right to die, according to Toronto's CBC News.

"We're all deeply concerned that this is a sad day for Canada," the cardinal told CNA on Thursday.

Although people see assisted suicide as a "simple solution," he said they will only begin to realise that "this is not the way to go."

"The very people who are most involved in helping people by the bedside while they are dying or while they are suffering are the ones most opposed to killing those entrusted in their care," said Collins.

The cardinal has been lobbying against the legalisation of the bill, suggesting to the government to "provide palliative care" for every Canadian, greater support for those with mental illness and help for those tempted to suicide" instead of providing ways to hasten death.

He earlier said that it is unfair for the government to force doctors at publicly funded hospitals to act against their conscience.

He added that it is "religious discrimination" to force the medical people to do it, according to CBC News.

In a video posted earlier this week on YouTube, Collins called on the federal government "to protect the vulnerable and those who care for them."

"Dying is simply not the same as being killed," he said, adding that "it is never justified for them to kill."

On Tuesday, Cardinal Collins said opponents of legalisation, including Evangelical Protestants, Jews, Muslims and the Salvation Army will hold a press conference on Parliament Hill in Ottawa, the Canadian capital to press the government anew to respect the sanctity of life.

The gathering would say to Parliament: "Thus far and no further. This is just not right. It's not right," he said, characterising the effort as "the ecumenism of practical love."