The retail giant Tesco, pictured, could be fined up to £200,000 after the arrest of suspected illegal workers at one of its warehouses
At least seven Tesco employees, who have not yet been identified, have since been deported and several others are still under investigation.
While those arrested, believed to be aged over 18, had student visas and the right to work in the UK , they are alleged to have exceeded their 20-hour-a-week working limit by up to a further 50 hours in some cases.
Tesco now face a bill of up to £10,000 per illegal worker - a total of £200,000 - for the breaches, unless the company can prove it carries out the legally required checks.
A UK Border Agency spokesperson said: 'We received information that some staff members were working in the UK illegally at Tesco.com on Factory Lane, Croydon. In response officers carried out an operation in full cooperation with the company shortly after 3am on Saturday, July 21 2012.
'Twenty 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.'
'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.'
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