Wal-Mart’s UK store sparks coupon stampede

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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.

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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.

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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.

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