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Wal-Mart’s UK store sparks coupon stampede

Jason Alden | Getty Images

Savvy shoppers across Britain are anxious to see if their Asda grocery deliveries will arrive on Friday, after cashing in £50 ($80) vouchers accidentally issued by the supermarket.

The Wal-Mart-owned chain launched a deal on Thursday which gave shoppers £50 off online grocery orders.

Bargain-hunters were quick to take advantage of the offer, adding £50 worth of goods to their basket, and paying only for the delivery charge. News of the deal went viral on Twitter – with hashtags including #AsdaGate and #SupermarketSweep becoming popular - and the Asda website crashed as a result of the traffic.

But it wasn't long before Asda - which has the second-largest grocery market share in Britain, according to Kantor Worldpanel - realized its mistake, and started cancelling orders that had used the voucher code.

On Friday morning, a spokesperson for the supermarket told CNBC it would not be honouring any outstanding orders which had used the "rogue voucher code."

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"We're aware of a glitch with our e vouchering, and are in the process of addressing it," the spokesperson said. "No-one has lost out as a result of it, but a small number of savvy customers have taken advantage and got more money off than they should have."

Andrew Stevens, a senior retail analyst at Verdict Research, specializing in food and groceries, said Asda was completely within its rights to withdraw the offer and cancel deliveries – despite sending out confirmation emails.

"I'm sure that people whose orders have been cancelled aren't too disappointed – they were probably just trying their luck," he told CNBC.

Not all customers were happy, though, and a number called for a boycott of the supermarket on social media websites following the cancellation of their order.

Despite this, Stevens added that the issue was unlikely to affect the company's reputation in the long-term.

"This clearly got a bit out of control for Asda," he said. "But Asda has always been known its value – voucher or not – and still will be once this has died down."

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Some shoppers, however, were optimistic that at least some of their deliveries would arrive on Friday, having received no cancellation email from Asda.

By CNBC's Katrina Bishop. Follow her on Twitter @KatrinaBishop and Google+