The Harper government is bracing for international backlash to its proposed new law that would ban people in polygamous and forced marriages from immigrating to Canada, The Canadian Press has learned.

Citizenship and Immigration Minister Chris Alexander announced the legislation Wednesday, calling such practices "incompatible with Canadian values."

The Conservative government promised in its 2013 throne speech to take steps on forced marriages and so-called honour killings.

If it becomes law, the bill would eliminate early and forced marriages from Canada's immigration system and the country as a whole, said Alexander. The measures would not include arranged marriages.

There are "at least hundreds" of cases of immigrants in polygamous marriages in Canada, the minister added.

The bill responds to cases in which Afghan men in Canada were accused of killing female relatives. Alexander said provisions in the bill will do away with the ability of perpetrators in such cases to use provocation or cultural differences as a mitigating factor.

But the "Zero Tolerance for Barbaric Cultural Practices Act" might not go over so well in some Arab and African countries, suggests an internal government briefing note, obtained by The Canadian Press.

The memorandum dated Oct. 27 and stamped "Secret," notes that polygamy remains legal in dozens of countries.

"This new admissibility provision related to polygamy, even with the availability of tools to mitigate impact, will certainly create bilateral irritants since polygamy is recognized under civil law in 50 countries (e.g. United Arab Emirates) and under customary law in 12 countries (e.g. South Africa)," said the document.

"This could also lead to reciprocity-related decisions by partner countries."

In the case of the U.A.E., negative fallout could undo three years of hard work by Foreign Affairs Minister John Baird to repair what had been a damaged relationship.

When Baird became foreign minister in 2011, relations with the influential Gulf state were in tatters.

It started when Canada wouldn't give two emirate airlines extra landing rights they were seeking. The government was trying to protect Air Canada.

The U.A.E. retaliated by kicking the Canadian Forces out of one of its military bases, a key staging ground for the Afghanistan mission. It also imposed a hefty visa charge on Canadian travellers.

Baird has since worked hard to repair relations, making numerous trips to the U.A.E. and welcoming his counterpart to Canada.

The internal memo says the Foreign Affairs and Immigration departments "will work closely to develop an engagement strategy with bilateral partners to not only make them aware of impending changes, but also to mitigate the expected negative impact of this tabling of the bill and its expected rapid coming into force."

Asked for further details, Baird's office deferred to Alexander's office, which did not immediately have a response about the engagement strategy.

The bill would amend the Immigration and Refugee Protection Act, making permanent residents or temporary residents inadmissible if they practice polygamy in Canada.

The bill would also amend the Civil Marriage Act to ban marriage for anyone under the age of 16.

It also changes the Criminal Code to impose a maximum five-year prison term on anyone who "celebrates, aids or participates" in a marriage rite or ceremony knowing that one of the persons is being married against their will, or is not of legal age.

Alexander noted the case of an Afghan immigrant accused of stabbing his wife to death last year, apparently because he felt dishonoured by her independence.

He cited another case in which an Afghan-Canadian man, his second wife and their son were convicted of first-degree murder in the deaths of his three teenaged daughters and his first wife — also because he felt they were bringing dishonour on the family by dating or dressing in ways he found offensive.

"Honour-based killings are nothing more than murders," Alexander said.

"We will be working through this bill to make sure that such killings are considered the murders that we know them to be. There is absolutely no room for ambiguity."

The 2013 speech from the throne promised action on forced marriages and so-called honour killings, an issue that has concerned the Harper government, in light of cases including the multiple murders in 2009 of female members of Montreal's Shafia family.

“Sadly, millions of women and girls continue to be brutalized by violence, including through the inhumane practice of early and forced marriage. This barbarism is unacceptable to Canadians," the throne speech said.

A government source says that globally, between 2004 and 2014, an estimated 100 million girls, will have been forced to marry before their 18th birthdays, often in polygamous unions.