Immigration Minister Jason Kenney says his government is working to crack down on bogus "marriages of convenience," which some people use to enter Canada.

However, he acknowledges that once people make it into the country, it can be very hard to get them out, even after they abandon a new spouse.

"That's why we need to focus on preventing them from getting to Canada in the first place," he said at a citizenship swearing-in ceremony in Ottawa.

"We've created a network of experts in anti-fraud, called migration integrity experts. We've increased the number of interviews we're doing abroad," he said.

A CBC News investigation recently learned Canada had only eight border officials investigating marriage fraud.

Kenney said enforcement of marriage fraud is up to the Canada Border Services Agency, but added his government has asked the agency to make the issue a priority.

He added that there is an element of personal responsibility, too, for Canadian citizens.

'Be very prudent'

"There's the Canadians who are vouching for the foreigners, and sometimes they'll even appeal a negative decision," he said.

"So we ask people: 'Be very prudent, be very careful.' If you suddenly fall in love with someone overseas, be very careful before you decide to sponsor them to Canada," he said.

Kenney said the government is also considering changes to the law.

That could see Canada follow the examples of the United States, Australia and the United Kingdom by introducing a waiting period of two to three years before a sponsored spouse could be come a permanent resident of Canada.