Employers have been warned of the risks of taking on staff from new EU accession countries Bulgaria and Romania who do not have permission to work in the UK.
Government restrictions effectively mean that employers will be prevented from taking on workers from these countries, said law firm DWF, except for workers classed as highly-skilled or 20,000 who will be allowed to work on farms or in food processing.
However, the self-employed will be able to work here, the firm added.
Although Bulgaria and Romania are due to join the EU on January 1st 2007, employees from these countries will be restricted in their right to work in the UK, unlike Polish and other accession countries' nationals that joined in 2004.
Employment lawyer with DWF Ansar Ali said: "The rules make it very difficult indeed to employ people from Bulgaria and Romania and could encourage a rise in illegal employment. Companies who are caught doing this could face stiff penalties."
Mr Ali advised businesses thinking of employing foreign nationals to always check they have permission to work in the UK to do the job offered and if offering a job to a highly-skilled individual without a permit, to allow sufficient time to apply for one.