Employers hiring illegal workers could find themselves paying on-the-spot fines of up to £2,000 according to new government proposals.

However, the system will be enforced by only 12 immigration officers, at an annual cost of less than £500,000, which has prompted claims that the new laws, unveiled this week, will be hard to police.

A new offence of "knowingly employing an illegal worker" will be created under the bill, and persistent rogue employers could face prison terms of up to two years and unlimited fines.