The cost of food and drink in retail stores has taken centre stage in the current Brexit debate.

Speaking out on behalf of the Remain campaign, Prime Minister David Cameron has warned that the cost of a weekly shop would rise by almost 3% if Britain left the EU.

A vote to leave would add £123 a year to the average family’s food and drink bill, said the Prime Minister, who visited a West London Asda with former deputy Labour leader Harriet Harman MP over the weekend.

“The last thing anybody wants is their food prices to go up,” Harman said.

“Going out of the EU, especially when so many of our goods come from the EU, would increase people’s food prices.”

But responding to the Prime Minister’s comments, Vote Leave chief executive Matthew Elliot said: ”As independent experts have found, the EU pushes up the prices in our supermarkets because of its protectionist policies. That’s ok for big business fat cats but it’s not good for British families.”

The PM’s warning came on the same day that a high-profile group of former supermarket bosses spoke out about the dangers of leaving the EU in an open letter to the Mail on Sunday.

Entering the fray, the former leaders of Tesco, Sainsbury’s, Marks & Spencer and B&Q said that leaving the EU would have a devastating effect on the economy.

“Like the leave campaigners, we believe Britain is a truly world-class country. But unlike them, we believe an exit could be catastrophic for the consumer recovery on which so much of our economic stability depends,” Sir Terry Leahy, Justin King, Marc Bolland and Sir Ian Cheshire said.

“It is impossible for us to see how there could be an exit without an impact on prices and inflation, the strong relationships we’ve built with our EU supplier partners, and the broader innovation and digital agenda.

“The unintended consequences of a leave vote and the uncertainty it would create would be a massive shock to the system. It would probably mean further depreciation of the pound, driving up the price of imported goods for consumers.

“A vote to exit would necessitate a complete renegotiation of our trading arrangements, which can only be of detriment to UK consumers,” the letter concluded.

The ex retail bosses also argued that a leave vote would lead to a spike in inflation, job losses, and a plunging pound.

The EU referendum takes place on 23 June.