Thousands of temporary foreign workers could be heading to airports to leave Canada today as permits expire for those who have been in the country for more than four years.

The Conservative government set April 1, 2015 as the deadline for temporary foreign workers in low-skilled jobs to either become permanent residents or leave the country after changing the rules in 2011.

In Alberta alone, 10,000 temporary foreign workers have applied to stay in Canada.

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(What is the temporary foreign worker program? Read The Globe's easy explanation)

Vancouver immigration lawyer Richard Kurland says there aren't enough Canadian Border Services agents to knock on the doors of every temporary foreign worker and frog-march them to the nearest airport today.

Nonetheless, he says, many of his clients are grappling with the realization that they're no longer welcome after living and working here for years.

NDP MP Jinny Sims says the deadline will likely force many workers underground.

She called the federal government inhumane for failing to allow the workers to stay in Canada while they're waiting to hear if they've been granted permanent residence.

"The Conservatives ignored all the warnings that their deadline was going to have unintended consequences and now some consultants have taken advantage of desperate temporary foreign workers, bilking them of their life savings while making false promises," she said Tuesday in the House of Commons.

Immigration Minister Chris Alexander replied that the temporary foreign worker program "is putting Canadians first."

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He added that "permanent residents have never been more numerous."

Several organizations, including the Canadian Federation of Independent Business, have called for an easier path to permanent residence and eventually citizenship for temporary foreign workers, especially those employed in provinces with labour shortages.

They warn that hotel rooms won't be cleaned and the lineups at fast-food restaurants will move a lot more slowly with fewer foreign workers.

Citizenship and Immigration Canada hasn't divulged the total number of TFWs about to be sent home, but immigration and labour market experts have estimated tens of thousands of workers could be affected.