Businesses in Yorkshire have been landed with fines worth almost £1.7m this year for employing illegal immigrants as cheap labour.
More than one in three companies raided by the region's immigration officials during 2010 were found to have hired foreign workers illegally.
The illegal workers were among more than 1,350 immigrants in Yorkshire who were removed from the UK following investigations by the UK Border Agency (UKBA).
Some 1,500 UKBA operations were carried out across the region during the year, including campaigns to stop sham marriages and people trafficking, as well as raids at factories, restaurants, car washes and off-licences.
UKBA regional director Jeremy Oppenheim said: ""Our operations targeting immigration offenders are all part of a crackdown to reduce the attractiveness of the UK to illegal immigrants.
"Anyone who employs a foreign national without permission to work here is breaking the law, undermining law-abiding businesses and could face a financial penalty.
"This year alone, we've issued penalties worth nearly 1.7m to businesses across Yorkshire and the Humber and that total will rise.
"We carry out immigration raids outside businesses – such as visits to home addresses and joint operations with the police – so offenders in Yorkshire and the Humber have no place to hide."
The operations were carried out by local immigration teams based in Hull, Leeds and Sheffield, whose work can range from catching criminals to helping police and councils investigate businesses who evade tax or breach environmental regulations.
UKBA officials raided more than 560 Yorkshire companies this year and found 187 were employing foreign workers illegally.
Businesses face fines of up to 10,000 for each illegal worker if they are unable to prove they carried out proper checks before hiring.
Seven workers at a samosa factory in Leeds were arrested earlier this month after checks showed they had no permission to work or remain in the UK.
Three Malaysian women, aged 27, 32 and 59, and a Bangladeshi woman, 39, were held after being found to have overstayed their visas, while three Pakistani men, aged 21, 57 and 65, were detained for a range of immigration offences.
On November 2, three Chinese men were found working illegally at a restaurant in Hull. Two were deported while the other was bailed but told to report regularly to UKBA.
At a Bradford restaurant, raided on September 30, officials found seven men from India and Pakistan working illegally. Two have been deported, two remain in detention awaiting removal from the UK, and the other three are "on report".
Sting operations in York, Selby and Rotherham in May uncovered illegal practices at three restaurants, two car washes and an off-licence.
UKBA arrested 11 men, who came from China, Pakistan, Turkey, Iraq and Afghanistan.
Regional immigration crime teams swooped on Sheffield Register Office, where 27 people were arrested on suspicion of being involved in sham weddings, and the former Rajput restaurant in Harrogate, where a people-trafficking investigation resulted in three owners receiving jail terms totalling 11 years.
Immigration Minister Damian Green said: "Since May we have delivered major changes to the immigration system including, for the first time, the introduction of a new limit on the number of economic migrants able to come to the UK.
"The UK Border Agency has undertaken two major enforcement campaigns to crack down on immigration crime in Yorkshire, detaining, prosecuting and removing people and gangs who have been abusing the system through sham marriages, illegal working, people smuggling and document fraud.
"We are making more use of new technology both at the border and inland to enable officers to focus their efforts on people trying to cheat the system."