Jake Hurfurt, Big Brother Watch’s head of research and investigations, said: “It is astounding that Tesco’s CEO wants to use this data to tell us how to live our lives. 

He said: “Mr Murphy’s comments should alarm everyone and serve as evidence that loyalty card schemes are based on mass-scale surveillance of customers. Tesco has no right to make judgements about what’s in our baskets or nudge us on what we should and should not be buying.”

NatWest last year sparked backlash after it started telling customers to stop eating meat and to drive electric cars, having combed through their accounts to calculate their carbon footprint. The bank at the time argued this was an opt-in feature. 

Tesco stressed it was not currently looking at rolling out a nudge policy. However, the potential for the company to intervene – either through messages at the tills or emails after checkout – is significant.

Tesco is by far Britain’s largest supermarket, holding almost a third of the UK grocery market. More than 20m people are currently signed up for the supermarket’s Clubcard scheme, which launched in 1995 and gives customers access to better deals. 

The suggestion that Tesco could use Clubcard data to nudge customers into making healthier choices in the future follows pressure from regulators for supermarkets to do more to help with obesity in the UK.

In 2022, the government introduced rules forcing grocers to move junk food away from prominent parts of their stores such as entrances and near checkouts. 

Sir Keir Starmer is plotting a series of further interventions on public health in a bid to help save the NHS from collapse. These include a ban on energy drinks for children under 16, which is expected to be introduced to Parliament next month, and supervised tooth-brushing rolled out for pre-school children later this year.

Critics have been warning that Britain is moving towards becoming a “nanny state”.