Asda customers are being advised to study their receipts after infuriated shoppers noted significant discrepancies between prices advertised on the shelf and at the till.

Sean Clegg was among those stung after using Scan & Go at the Gravesend store.

He says he has noted mark-ups of up to £1 on individual items when shopping at his branch, in Thames Way, after using the technology.

The differences have also been reported at the grocer's stores in Strood and Greenhithe, and are also affecting regular shoppers paying at the tills at the end of their shop in the traditional way.

Scan & Go technology allows customers to scan their products when picking them up off the shelf, where the price is immediately displayed, and then pay directly through the app or a dedicated kiosk.

But Sean says every week he is becoming increasingly infuriated at the discrepancies between the prices quoted on the machines and those on the labels.

In one trip alone, last week, he photographed five items being sold for a higher price than advertised – a total of an extra £2.15.

They included washing powder showing at 80p more than the scanner price and cheese at 75p above the advertised rate.

Pepperoni, spaghetti loops and bacon were also showing discrepancies.

Sean said: "The stated ticket price on the shelf is different from the actual price you pay. I spotted it on five items in one shopping session.

"I would have bought them and been totally unaware of the first one had it not caught my eye.

"There is probably a multitude of other mispricing around the shop, which if you were using a manned check-out you may not notice.

"It annoys me that if anyone didn't have the means of checking they would be paying more than expected.

"And in these times of hardship it's very unfair on the families that are struggling and have to shop on a budget."

He wasn't the only one to have spotted the price hike.

Mum Karren Niblett, also from Gravesend, said: "I've told staff several times over several months about advertising the wrong prices. Evidently it falls on deaf ears.

"All I do now is take pictures of the advertised price and show the checkout person and they cancel the item and change it to the advertised price. It's getting to be a joke now though.

"All prices are increasing by 25p, 50p or 75p now. Such a hike is more than the odd penny here and there.

"I have to buy lactose-free items and the prices were going up but they weren't advertising the correct price. I was telling staff for at least three months."

Karren, says she now uses her Asda app to scan her shopping to keep a firm eye on each item as she scans.

The price discrepancies have driven some shoppers to take their custom elsewhere.

They include Hayley Davis, also from Gravesend, who said: "I try to stay away. The tickets are often wrong or there are no prices on the shelves," she added.

"They are meant to have staff go round in the mornings changing tickets but all stores just say the same: 'We don't have the staff'.

She added: "There seem to be so many issues with the supermarkets these days. They just don't have enough staff to keep on top of everything."

Armed with a Scan & Go device we sent out our reporter Keely Greenwood to visit Asda's stores in Gravesend, Strood and Greenhithe where price discrepancies had been reported.

She scanned 10 items of varying prices in the Greenhithe and Gravesend stores but found no disparities.

However, after scanning another 10 items in the Strood store she found one where the price on the scanner was 50p more than the price stated on the shelf.

It did not correct itself at the checkout and so she asked an assistant who manually over-rode the price.

She also tried buying the product, a carton of Tropicana, in the usual way by taking it to a till without using Scan & Go and found the item was, again, being sold for more.

A spokesman for Asda said: “The process of price changes mean that shelf edge labels should be changed at the same time as they are updated on Scan & Go.

"If an item scans at a different price as to that shown on the shelf edge label, the customer should alert a colleague who will be able to confirm the correct price to be paid.”