Dozens of people have been arrested in a crackdown on nail bars suspected of committing immigration offences.
A total of 97 people were arrested, while businesses were warned they could face fines of up to £20,000 per illegal worker. Some 14 people were also identified as potentially being at risk of modern slavery.
The week-long Operation Magnify aimed to target risk industries in which ministers claim employers are exploiting foreign workers.
The Immigration Enforcement initiative took place from 27 November to 3 December and saw officers visit more than 280 businesses across the UK. It comes after Theresa May promised tougher immigration rules in her first conference speech as Conservative leader.
Immigration minister Robert Goodwill said: “This operation sends a strong message to those employers who ruthlessly seek to exploit vulnerable people and wilfully abuse our immigration laws.
Modern slavery is a barbaric crime which destroys the lives of some of the most vulnerable in our society.
This Government has taken world-leading action to tackle it by introducing the Modern Slavery Act, giving law enforcement agencies the tools they need and increasing support and protection for victims.
At the same time, we have also introduced strong measures through the Immigration Act to tackle illegal working, including making it easier to prosecute employers who repeatedly break the rules and creating the power to temporarily close businesses that do not comply with the law.
The majority of the 97 people arrested were Vietnamese nationals, but the number also included suspected immigration offenders from Mongolia, Ghana, China, Nigeria, Pakistan and India.
Those who are potential victims of trafficking will be offered support, while those who have no right to be in the UK will be removed, the Home Office said.
Officers also issued notices to 68 businesses warning them they may be liable for financial penalties of up to £20,000 per illegal worker found if they cannot provide evidence that appropriate right to work document checks were carried out.
Fourteen people were referred to the National Referral Mechanism hub, which supports those identified as possible victims of slavery and human trafficking.
The operation also focused on the construction, care, cleaning, catering, taxi and car wash industries during 2016, with further activity in similar sectors planned for 2017.