The government has named and shamed 37 firms - including H&M, Kings Group and Welcome Break - for failing to pay staff the national minimum wage.
According to the Department for Business, Innovation & Skills (BIS), the firms will be fined a total of £51,000 and must also pay affected staff the £177,000 they were underpaid.
It is the single biggest list of companies exposed for underpaying staff by BIS after it already named 55 firms since October 2013.
Business minister Jo Swinson said paying less than the NMW was illegal, immoral and completely unacceptable.
“If employers break this law they need to know that we will take tough action by naming, shaming and fining them as well as helping workers recover the hundreds of thousands of pounds in pay owed to them.
“We are also looking at what more we can do to make sure workers are paid fairly in the first place. As well as being publicly named and shamed, employers that fail to pay their workers the National Minimum Wage face penalties of up to £20,000. We are legislating through the Small Business, Enterprise and Employment Bill so that this penalty can be applied to each underpaid worker rather than per employer,” she said.
The minimum wage for adults aged 21 and over currently stands at £6.50 per hour.
The three major Westminster parties have all said they want to raise it.
Fashion retailer H&M (Hennes & Mauritz) failed to pay £2,604.87 to 540 workers but blamed “time logging errors” for the underpayment. All arrears have since been processed and the business has accepted that the errors should not have occurred.
HMRC said they were happy with H&M's transparency, cooperation and full engagement with the process.
Welcome Break also failed to pay £1,318.70 to 20 people and said a new IT problem contributed to the mistake.
The motorway service station company said the initial breach was brought to light as an employee complained to the HMRC that her pay rate had not been increased correctly upon reaching her 21st birthday. After investigating, it found more people in a similar position.
The mistake resulted from a combination of factors, the firm said, including a change of management within the units, periods of holiday and difficulty with its new IT system.