Legislation that would dramatically expand the powers of Canada's spy agency has cleared a key hurdle.

The House of Commons on Wednesday approved the Anti-Terror Act, which was spurred by last year's attack on parliament.

The act would give the spy agency the ability to operate overseas and make preventative arrests.

Dominated by the Conservative party, the Senate is expected to approve the act before June.

Prime Minister Stephen Harper has been a staunch supporter of the bill, which criminalises the promotion of terrorism, including via the internet.

"There is a high probability of jihadist attacks from within," Canadian Defence Minister Jason Kenney said. "The threat of terrorism has never been greater."

The bill also makes it easier for police to arrest and detain individuals without charge.

Critics who say the bill is overly broad and lacks oversight had sought to make changes but their attempts failed.

Four former Canadian prime ministers and five justices of the Canadian Supreme Court have written public letters questioning the bill.

"This bill will almost certainly lead to a chill on freedom of speech," said Allan Weiss, professor of humanities at York University. "It is filled with vague wording that would make it possible for the government to label virtually anything it disagreed with as harmful to Canada's national interests."

In October 2014 a gunman shot and killed a soldier at the National War Memorial in Ottawa and then attacked Canada's parliament buildings nearby.

Two days before, a man said to be inspired by the Islamic State group ran over two soldiers in a car park in Quebec, killing one and injuring the other before being shot dead.