The ‘round up your shop’ initiative runs until Sunday 13 September and encourages shoppers to donate money to charity by rounding up their shopping to the nearest £1.

But shoppers have reported their bills being rounded-up without their consent and it’s only once they’ve got home and checked receipts that they’ve seen the ‘charity round up’ donation.

One Twitter user posted: “I give regularly to charity but having money taken without my knowledge or agreement is theft. I will be boycotting Tesco from now on.”

Another wrote: “I didn’t know about this ’round up’… until I got in from shopping and saw it tagged on the bill. The checkout person was deaf and not able to talk, no fault of their own. However, in these financially difficult times, perhaps put some signage, so there’s a choice.”

And another posted: “Shame you didn’t advise my elderly mother of this she only realised when she left the store and was not given the option!!!!”

Money raised from the initiative will be split between Cancer Research UK, British Heart Foundation and Diabetes UK.

A Tesco spokesperson, said: “To support our health charity partners at this critical time, we are encouraging our customers to round up the cost of their shopping to the nearest £1. Customers will be asked if they would like to donate by one of our checkout colleagues when they pay for their shopping or on-screen if they are using a self-service till.

“We also have signs in our stores letting customers know about the campaign and how they can support it. The response to the campaign so far has been overwhelmingly positive with very few customers feeding back that they were not aware that they had made a donation.”