HM Revenue and Customs (HMRC) has targeted job agencies in Corby in a minimum wage crackdown.
A three-day operation uncovered a possible £100,000 owed to 3,000 employees in the area.
Officers from HMRC and the Department for Business, Innovations and Skills (Bis) visited 34 employment agencies between 28 and 30 May 2013.
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HMRC can issue penalties of up to £5,000 to employers found to be paying their workers less than the national minimum wage (NMW), which is currently £6.19 per hour for adults.
Employers will also be required to pay any wage arrears at today’s NMW rates.
Michelle Wyer, assistant director of national minimum wage at HMRC, said: “This cross-government taskforce operation has allowed us to get into the heart of the community to tackle those employers that operate outside of the law and deliberately fail to pay the NMW.
“We will not hesitate to use our full-enforcement powers to ensure that workers receive the money to which they are legally entitled.”
Jo Swinson, employment relations minister, added: “I fully support the joint approach being taken by these enforcement bodies.
“The advice and guidance given by our investigators on these visits made sure that agencies are fully aware of their legal responsibilities and what they need to do to abide by the law.
“We want to make sure that the employment rights of vulnerable agency workers are protected and create a level playing field for that vast majority of agencies who play by the rules.”