Supermarket Tesco has confirmed today that it has called in police after customers using its Clubcard loyalty scheme raised concerns of possible online fraud.

A number of shoppers contacted the retailer after discovering hundreds of pounds worth of vouchers were missing from their accounts, while others complained of being unable to log on to their accounts online.

While Tesco has not confirmed how many of its customers have been affected by the issue, Retail Gazette understands that the number is a very small proportion of its 16 million Clubcard users.

Last month, pressure group the British Retail Consortium revealed in its Retail Crime Survey 2012 that online crime made up 37 per cent of the total cost of retail crime last year and this latest news will heighten awareness of the need for increased security measures.

The grocer urged any customers who fear they may have been affected to get in touch with its Clubcard customer service team as reassuring shoppers is a priority.

A statement from Tesco said: “We have launched a thorough investigation into a small number of incidents and referred the matter to the police.

“In the meantime, we‘d like to ask any customers who believe they‘re affected to contact us directly so that we can make sure their accounts are up to date.”