The federal government gave companies across Canada approval to hire temporary foreign workers for less than market wage in 2013, the Alberta Federation of Labour says.

it has obtained internal government documents that show Ottawa sanctioned companies to underpay temporary foreign workers last year, despite rules requiring employers to pay foreign workers the prevailing market wage for their region and skill set.

According to the documents, 3,700 foreign workers were paid less than what a Canadian would earn, with more than 2,100 positions in Alberta alone. According to the documents, temporary foreign workers were brought in to fill positions in at least a dozen different sectors, including trucking, health care, and automotive mechanics.

In a statement, Alberta Federation of Labour president Gil McGowan said the documents are a 鈥渟napshot鈥� of what was taking place as the Harper government attempted to reassure Canadians that they were taking steps to improve monitoring and rules enforcement within the troubled workers program.

鈥淏ehind closed doors, they knew the rules were being bent and broken, and they knew thousands of TFWs were being underpaid and used as pawns to drive down wages for all Albertans,鈥� McGowan said.

The union head also said the documents show that misuse of the Temporary Foreign Worker program extend 鈥渇ar beyond鈥� the food-service industry. In April, Employment Minister Jason Kenney imposed a freeze on foreign workers in the food-service industry following allegations that some McDonald鈥檚 franchises were bringing in too many low-paid labourers.

Nearly two months after the suspension, Kenney announced a crackdown on the TFW program that included a cap on low-wage workers and heavy fines for employers who break the rules.

In an interview with CTV Calgary Friday, McGowan said Canadians who are looking for 鈥渄ecent鈥� jobs and wages should be 鈥渟hocked and appalled that their federal government has been using their power to help employers essentially defy the economic laws of gravity and keep wages down when objective conditions say those wages should be going up.鈥�

In a statement, Jason Sinclair, spokesperson for Canada Employment and Social Development, said that prior to April 2013, 鈥渆mployers were allowed to hire a temporary foreign worker below the prevailing wage if the employer could prove that there was a Canadian being paid the same wage for doing the same job at the same location.鈥�

However, the federal government can鈥檛 say with absolute certainty that the wage disparity didn鈥檛 happen beyond that time.

With a report from CTV Calgary鈥檚 Scott McLean