New supermarket “challenges” that reward shoppers with extra loyalty points for buying more could lead to overspending, consumer groups have warned.

Four of the UK’s biggest supermarkets – Tesco, Sainsbury’s, Asda and Morrisons – are now offering members of their loyalty schemes bonus points if they hit spending targets.

The supermarkets all say their schemes offer customers better value and more personalised savings.

But consumer group Which? and debt charity StepChange warned that setting shopping challenges could encourage people to spend more than they can afford.

These challenges are the latest development in supermarket loyalty card schemes which are becoming ever more sophisticated.

At the same time, food prices were rising at an annual rate of almost 20% last year – the highest since the 1970s – and are only now returning to “more normal” rates.

“Competition between supermarkets is fierce at the moment, with all of them shouting about the number of prices they’ve dropped,” said Ele Clark, retail editor at Which?. “But the fact remains that overall food is still far more expensive than it was a couple of years ago.”

Ged Futter is a former buyer for Asda and now advises suppliers on how to negotiate with retailers. He said personalised prices and challenges were simply a way for supermarkets to compete for customers.

“They’ll look at products you buy during the course of the month and then they will give you offers to make sure that you buy that product again with them,” he said.

The challenges vary between supermarkets and involve shopping more frequently or hitting a spending target on specific products within a set timeframe.

Jo Rourke, a single mum-of-three from Manchester, told the BBC shoppers “need to act with caution” when it comes to loyalty card challenges or missions.

“The terminology of ‘challenges’ could make it feel like a game and if you are someone who gets drawn into this kind of thing it could be quite dangerous,” she said.

Ms Rourke – who shares tips on how to save money on the food shop on her @thismumcooks social media accounts – said she did not think supermarket challenges would encourage her to do more of her shopping in one store.

“I don’t think it pays to be a loyal customer. I think it pays to shop in all of the supermarkets in your area,” she said.

The average person has loyalty cards for three supermarkets, data from research firm Kantar suggests.

• Learn prices: Get to know the cost of the items you buy regularly so you can spot what is a good offer and what is not
• Compare price per 100g: Look along the shelf at similar items as loyalty prices might not be the cheapest option.
• Set a budget and stick to it: Often supermarket vouchers or challenges will require you to spend more so don’t be tempted to overspend
• Stock up: If you do want to take advantage of a money-off voucher then bulk buy staples like pasta, rice or tinned food that have a long shelf life
• Use tech: Use independent supermarket comparison apps to save your favourite items and get alerts when they go down in price

Ms Clarke at Which? told the BBC: “With many families struggling to make ends meet, it’s important supermarkets don’t go overboard with these challenges and encourage shoppers to spend beyond their means in order to access rewards.”

The consumer group has previously claimed Sainsbury’s and Tesco loyalty card prices were not as good as they seem. The Competition and Markets Authority announced a review of loyalty pricing by supermarkets in January 2024.

It is examining whether loyalty prices are a genuine promotion or could mislead shoppers, if they put any groups at a disadvantage and whether they impact shopping habits and how supermarkets compete with each other. An update on its findings is expected in July.

Simon Trevethick, head of communications at StepChange, said: “While retailer loyalty schemes can provide helpful discounts for customers, there’s a risk that if spending is incentivised, people may end up spending more than they had initially planned or can afford.” He urged anyone in financial difficulty to contact the charity.

The BBC asked Tesco, Sainsbury’s, Asda and Morrisons for their response to concerns that their loyalty challenges could encourage overspending.

A Tesco spokesperson said its challenges were “all about rewarding customers for buying the products they regularly purchase”.

Sainsbury’s said bonus points were “issued based on the number of shops customers complete, with a minimum qualifying spend of £1 per shop”.

Asda and Morrisons did not respond.