Liberal MP Justin Trudeau said the government should not call honour killings "barbaric" in a study guide for would-be Canadian citizens.

On Monday, the federal government updated its Discover Canada guide, a pamphlet given to new immigrants to help explain life in Canada and prepare them for the citizenship test.

Among other things, it tells new Canadians that gay marriage is OK and forced marriages are not.

But the guide also says: "Canada's openness and generosity do not extend to barbaric cultural practices that tolerate spousal abuse, 'honour killings,' female genital mutilation, forced marriage or other gender-based violence."

"Those guilty of these crimes are severely punished under Canada's criminal laws," it reads.

Trudeau blasted the Conservatives for using the term "barbaric," even though it's been in the guide since 2009. Forced marriages are the only new item on the list.

"There's nothing that the word 'barbaric' achieves that the words 'absolutely unacceptable' would not have achieved," Trudeau, the Liberal immigration critic, said.