Tesco has pledged to take action after an investigation found customers were being short-changed on promotions which had expired but were still advertised on shelves.

The probe by the BBC’s Inside Out programme found that in 33 out of 50 stores visited by its reporter, multi-buy promotions were marked on the shelf, but the time-limited discounts were not applied at the checkout.  In some cases, the deals advertised on the shelves were weeks and even months out of date.

Martin Fisher from the Chartered Trading Standards Institute told the BBC that such mistakes could break the law by falling foul of The Consumer Protection from Unfair Trading Regulations 2008.  He suggested other supermarket chains could have similar issues, saying: “The underlying problem is that people don’t complain because they don’t realise. Very few people remember [the price] from the shelf to the till so complaints are extremely low.”

In every case where the discrepancy was brought to light, Tesco staff honoured the offer.  However, after reporters pointed out the discrepancies, some stores still failed to remove out-of-date labels.

As a result of the BBC’s investigation, Tesco has pledged to double check the accuracy of the price labels at all its 3,500-plus stores across the UK.

A spokesperson for Tesco said: “We take great care to deliver clear and accurate labels for our customers so they can make informed decisions on the products they buy. We are disappointed that errors occurred and will be working with the stores involved to reinforce our responsibilities to our customers”.

Vickie Sheriff, Director of Campaigns and Communications at Which?, commented: “To avoid confusing their customers, supermarkets need to be clear about how long offers are running for. We don’t want people to get a nasty surprise when they reach the till and find out the cost of the goods are higher than expected.”