Tesco customers are being overcharged by the grocer on expired offers that are still advertised on its shelves, according to a BBC investigation.

The Inside Out programme found that in 33 of 50 stores visited over a three-month period, the grocer was charging full price at the till on expired multi-buy promotion offers still advertised on the shelves.

The investigation found that multi-buy deals were sometimes being advertised on shelves in the supermarket’s stores for weeks and months after the discounts were no longer applied at the checkout.

Tesco said it would double-check the pricing of products across its UK store estate, which comprises over 3,500 shops.

A spokesperson for the grocer said: “We take great care to deliver clear and accurate price 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.”

All expired offers that were advertised were honoured in the stores featured in the investigation, which were located in the West Midlands, Liverpool and Leeds.

The discrepancy between advertised prices and those charged at check-out were only found in-store and not on Tesco’s ecommerce offer.

The Chartered Trading Standards Institute’s Martin Fisher said the problem could affect the wider industry, not just Tesco.

“There is no real idea of the level of the problem [in the wider supermarket industry] because it is not recorded in enough detail to be searchable,” said Fisher.

“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.

“I would really hope that Tesco are out there on their own on this. I would hope that other stores have better systems to check and feedback and learn from their customer complaints.”