Supermarket spending “challenges” could lead to shoppers overspending as they attempt to hit specific targets, Which? has warned.

The watchdog and debt charity StepChange have cautioned that supermarket loyalty schemes with bonus points for shoppers who hit certain spending targets could encourage people to spend more than they can afford, the BBC reported.

Currently four of the UK’s leading supermarkets -Tesco, Sainsbury’s Asda and Morrisons – offer a loyalty programme with spending-related bonus points.

The grocers argue that such initiatives give shoppers better value and offer personalised savings.

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A Tesco spokesperson told the BBC 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”.

However, Which? retail editor Ele Clark said: “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.”

It’s not the first time the supermarkets’ loyalty schemes have come under fire. Last year, Which? said supermarkets were opting for “potentially dodgy tactics on loyalty offers” to present the savings in the best light.

Which? tracked the pricing history of dozens of member-only offers at Tesco and Sainsbury’s over six months and found that almost a third (29%) of the exclusive promotions were at ‘regular’ price for less than half that time.

Earlier this year, the CMA started its review into whether UK supermarket loyalty pricing is misleading shoppers.

The investigation will consider factors such as if a loyalty price is a genuine promotion or as good as a deal is presented, and will look into whether any groups of shoppers are disadvantaged by this type of promotional activity.

The competition watchdog will also review whether loyalty pricing is impacting consumer behaviour and if it has an impact on how supermarkets compete with each other.