The Department of Immigration and Citizenship is encouraging businesses to ensure any employees they hire are legally entitled to work in Australia.

Yesterday 11 overseas nationals were sent to the Perth Immigration Detention Centre after they were found to be working and living in Australia illegally.

Department spokeswoman Cian Manton says there are a number of ways businesses can check they are complying with the law.

"We have a visa entitlement verification online service and basically that allows employers to check the relevant identification details of prospective employees and that means that they can be confident has the right to work in Australia and has a valid visa," she said.

"There are hefty fines of up to $20,000 and two years in jail for individuals, and companies face fines of more than $100,000 per illegal worker so the penalties are significant because it's a significant offence."