Supermarket chain Asda has been hit by a technical error on its website which allowed customers to claim for food vouchers worth thousands, it has been confirmed.

As part of its Asda Price Guarantee (APG) promise, customers receive money-off vouchers if their weekly shop was more expensive at Asda than at its main rivals, adding 10 per cent value to the vouchers as part of the scheme.

However, due to a computer glitch which saw the grocer undervalue it‘s competitors products, shoppers have been able to cheat the system and receive coupons offering more than they should, with social media platforms and forums set up to discuss how to take advantage of the mistake.

Although Asda said that only “a very small number of our savviest customers” were able to beat the system and claim additional vouchers, this will be a bitter blow for the chain at a time of considerable competition within the grocery sector.

Earlier this month, Kantar Worldpanel announced its supermarket share figures which revealed that Asda saw market share growth of 4.5 per cent in the 12 weeks to September 2nd 2012.

Last month, UK-based online grocer Ocado‘s CEO Tim Steiner announced a price war on rivals, highlighting the e-tailer‘s trial of its ‘Low Price Promise‘ which pledges to beat the price of any comparable Tesco‘s shopping basket.

In response to the computer error, an Asda spokesperson said that while saving customers‘ money is “in our DNA, unfortunately this is a gift that can‘t keep on giving”, adding that the value of the voucher was capped at £15 last Sunday.

Keen to emphasise that the error affected only a minority of shoppers, Asda said that only 0.24 per cent of its customers generate vouchers for over £15, meaning that few will have been impacted over the period.

A spokesperson said: “We‘re aware of a small glitch in the APG, and are in the process of addressing it.

“No-one has lost out as a result of it, but a small number of savvy customers have taken advantage and claimed a few, larger than normal, vouchers. We‘re in the process of removing the ability to do this.

“The tweaks we are making to the APG will have little or no impact on the vast majority of customers who can carry on using the APG to compare the cost of their weekly shop.

“We will continue to guarantee to be 10 per cent cheaper on a comparable basket of groceries than our rivals, or we will refund the difference.”