A “record” 649 people were arrested suspected of working illegally at businesses including car washes, nail bars, barber shops, takeaways across Wales last year, according to the UK government.
The Home Office said the arrests followed more than 1300 raids across Wales and the businesses were targeted as part of “sweeping reforms” to cut illegal migration.
The UK government says the crackdown is building on work to “restore order” to the immigration system and “end the lure” of illegal working that gangs use to sell spaces on small boats.
Welsh Secretary Jo Stevens said: “Illegal working fuels the black economy and hurts law-abiding Welsh businesses.”