The UK's Insolvency Service said its countrywide crackdown over the past few months had found that all 20 had already been fined for employing illegal workers.
Ashim Kumar Saha, a director of Save & Pick Limited in London, was disqualified and fined 10,000 pounds for employing one illegal worker.
Manoj Barua and Vipan Kumar Sharma, directors of MV Hospitality Limited which traded as a restaurant known as Caf India in Glasgow were disqualified for employing four illegal workers and fined 40,000 pounds.
Between them, they employed 41 illegal workers and were fined a total of 505,000 pounds by the UK Home Office, none of which was paid. Two of the companies have now entered into liquidation, with a further two having been dissolved.
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Cheryl Lambert, Chief Investigator at the Insolvency Service, said those caught sought an unfair advantage over law abiding competitors by employing people who were not entitled to work legally in the UK.
"By definition this is a set of people who are without the protection of the law and knowledge of the authorities, and thereby extremely vulnerable to exploitation in all its forms. It is bad for business and bad for society as a whole," she added.
The businesses caught up in the investigation, which include 11 restaurants, four takeaway/fast food establishments and a shop, are based in London, Sussex, North West, South Wales, Glasgow, Antrim, Frome and High Wycombe and cover South Asian and Chinese cuisines.
"It undercuts honest employers, cheats legitimate job seekers out of employment opportunities and defrauds the taxpayer. Businesses should be aware that they have a duty to check that their staff have permission to work in the UK," a spokesperson said.
The matters leading to all 20 disqualifications are that the directors failed to ensure that the companies complied with statutory obligations under the UK's Immigration, Asylum and Nationality Act 2006 to ensure that relevant immigration checks were completed and copy documents retained, resulting in the employment of illegal workers.
All were directors of the companies at the time of the Home Office visit.