Supermarket deals on smartphone apps could mean older and more vulnerable shoppers are being penalised by missing out on the best offers, experts warn.
High street stores are advertising their apps to customers in order to access exclusive loyalty schemes, which give shoppers access to the cut-price deals.
Retail analyst Mintel estimates that four out of five shoppers are signed up to at least one loyalty card scheme - which are predominately marketed through apps.
But experts say many of the older generation, who may not use smartphones or only rarely access the internet, could be paying disproportionately more for their weekly shop, The Telegraph reports.
Figures from charity Age UK reveal that a third of over 75s do not use the internet at all, amount to 1.6million people. Over two thirds of this age group also struggle with passwords and understanding how security checks work, meaning their internet usage is limited.
Loyalty schemes are shown to make significant savings for shoppers - but concerns have arisen that only those with digital access can benefit from them
Caroline Parkes, chief strategy officer at global marketing agency RAPP, said: 'Increasingly, offers are being pushed purely in the digital space.
'With such high levels of over-75s not using the internet, let alone having a smartphone or being able to understand how apps work, you've got a huge proportion of what can be a very vulnerable part of society who cannot get access to [certain deals].'
The Asda Rewards scheme is available only to shoppers who download its smartphone app, which allows customers 10 per cent off the retail price for selected items.
Lidl's dedicated app, Lidl Plus, is also reserved for smartphone users who can access money-off coupons based on how much they spend in store as well as enter competitions for vouchers.
Morrisons introduced its app in 2021, replacing its plastic Morrisons More loyalty cards. The brand has since allowed customers to apply for physical cards, but this must be done online or via the app - with a 14-day waiting period for the cards to arrive.
Tesco's Clubcard remains available as an app or card, but the firm is encouraging shoppers to use the digital version.
Dan Wilson, vice-president of supply chain consultancy firm Proxima, told the Telegraph that major retailers were keen for customers to install their apps because of the amount of data that can be harvested.
He said: 'They can see if the customer saw an offer and then acted on it and bought the product – apps help them close the loop.'
Among major supermarkets, Tesco and Sainsbury's now own huge digital media firms which use data from loyalty scheme members for advertising purposes.
In November last year, the Competition & Markets Authority watchdog launched an investigation into loyalty card pricing after concerns raised by the consumer group that supermarkets were using 'dodgy tactics' to try to get shoppers onto their schemes.
Tesco and Sainsbury's, which strenuously denied the claims, have significantly boosted their Clubcard and Nectar schemes with thousands of discounts across their ranges in an attempt to get more customers to sign up.
The chains are reported to be selling on their data for an estimated £300million a year to give other businesses insights into what typical people might want to buy in stores.
A basket of seven branded essentials at Tesco including Heinz beans, Anchor butter and Andrex toilet paper costs 19 per cent less with a Clubcard – while Nectar card holders at Sainsbury's can save 18 per cent, according to data from Assosia analysts.
Sainsbury's now has 18million Nectar card customers after gaining three million in the past 12 months, while Tesco's Clubcard total rose above 20million last year.
Asda, Tesco, Morrisons, Lidl and Sainsbury's have been approached by MailOnline for comment.
A Boots spokesman said: 'The Boots Advantage Card loyalty scheme is open to all, with customers able to choose the sign-up and card option that suits them best e.g. physical or digital.
'If a customer prefers not to sign up online or via the Boots app, a team member in any store can sign them up and provide them with a physical card or they can call our customer services team.
'In addition to price advantage which offers exclusive prices to Advantage Card members, Boots offers an extensive range of promotions that are available for all, helping customers to make savings on their health and beauty needs.'
Graham Wynn, of the British Retail Consortium, which represents retailers, added: 'Retailers are committed to providing value to their customers, and loyalty schemes, which are open to all, are one of many ways that retailers offer their customers genuine bargains on a daily basis.'