A lack of the correct UK visa checks cost businesses in the Plymouth area dearly last year.
Recent reports from the UK Border Agency (UKBA) revealed that a total of 15 businesses were caught employing illegal workers in 2010.
Altogether, their fines for the UK immigration crimes came to more than £100,000 for the year after 28 illegal workers from countries including China, India, Bangladesh and Afghanistan were found to be working without the correct UK visas.
The fines are imposed on the employers when it is shown they failed to conduct the correct UK visa checks on their overseas workers' documentation before hiring them.
Kenny Chapman, head of the UKBA local immigration team for the region, commented: "There is simply no excuse for employing illegal workers. There are basic checks that an employer can carry out to establish an individual's right to work in the UK.
"Where employers fail to make these checks we will not hesitate to take the strongest possible action."
He added that employing illegal workers undercuts honest businesses and defrauds the public of significant sums of money.
The Plymouth incidents were part of a wider operation across Devon and Cornwall last year, which resulted in 83 firms being charged with UK immigration crimes.
Civil penalty fines totalling £762,500 were handed to the offending companies, while 259 illegal immigrants from the region were deported.