The UK’s largest retailer, Tesco, is facing a fine of up to £200,000 for illegally employing foreign workers, The Telegraph reports.

20 foreign students of primarily Bangladeshi and Indian origin were arrested for working longer hours than their visas permitted, seven of whom has since been deported. Although the workers had the right to work in the UK, their visas were only valid for up to 20 hours a week during term time, and the students had worked between 50 and 70 hours. A further 15 students are undergoing investigation during the Home office crackdown on ‘visa abuse’ to which tesco is said to be ‘cooperating fully’ with the UKBA.

Authorities will now decide whether to issue the supermarket with a notification of liability (NOL) and a fine of up to £10,000 per illegal worker.

Tesco needs to provide “evidence that it was carrying out the legally required checks to avoid a fine” under Section 15 of the Immigration, Asylum and Nationality Act, introduced in February 2008.

A UKBA spokesman said:

“We received information that some staff members were working in the UK illegally at on Factory Lane, Croydon.

“In response officers carried out an operation in full cooperation with the company shortly after 3am on Saturday 21 July 2012.

“20 individuals have been arrested and now face removal from the UK.

“The operation was part of an ongoing campaign to tackle visa abuse which has seen over 2,000 offenders removed since the beginning of May.

“The employer now needs to provide evidence that it was carrying out the legally required checks to avoid a fine.”

A Tesco spokesman said:

“In cooperation with Tesco, the UK Border Agency visited our dotcom store in Croydon in July. As a result of this visit, a small number of staff were found to have breached the terms of their working visas.

“We continue to cooperate fully with the UK Border Agency as they look into this issue.

“We take our responsibilities as an employer very seriously and do not condone illegal working of any kind. We have a comprehensive system for ensuring all the correct procedures are followed in this area which has been externally audited and generally works well. We have now taken additional steps to ensure an incident of this nature does not happen again.”