A former premier of a Canadian province has said prime minister and fellow Conservative Stephen Harper is "bad for the country" because some of his policies are close to being racist.

Ex-Newfoundland and Labrador premier Danny Williams urged Conservatives not to vote for Mr Harper, who has made the Islamic face veil a focus of the October 19 election.

Mr Harper's government failed in an attempt to ban the practice of wearing the niqab while swearing the citizenship oath and lost an appeal on Monday to have the decision delayed while it appeals to the Supreme Court.

Just two women out of more than 650,000 people have chosen not to proceed to the citizenship ceremony based on the requirement to remove their face coverings.

"Two women have been in that situation. Why is that a national issue?" Mr Williams said.

The Harper government also said last week it would create a phone line for Canadians to report those engaged in "barbaric cultural practices" such as early and forced marriages.

Opposition leaders have condemned injecting religion into the election campaign. Conservatives "are playing with fire, and people are going to get hurt", Gerald Butts, a close adviser to opposition Liberal leader Justin Trudeau, tweeted last week.

Mr Williams said Mr Harper was pitting Canadians against each other and said the prime minister "doesn't care if he possibly crosses that racism line".