Fresh from attempting to shame Tesco for raking in £1bn profits during the cost of living crisis, consumer group Which? is back on the warpath today, this time taking aim at all of the traditional big four supermarkets.

The UK’s “consumer champion” released the results of a mystery shop claiming Tesco, Asda, Morrisons and Sainsbury’s are withholding their most affordable products from the many cash-strapped households who rely on local convenience stores for much of their weekly shopping.

The Which? site features a video of one team member discovering – to much amazement – his local Sainsbury’s convenience store fails to carry the budget range on offer in its larger superstores and sprawling hypermarkets. His shock is compounded when he realises the products on sale in such c-stores are also more expensive than in the bigger stores.

To directly compare the ranges in large stores and convenience stores completely ignores the profoundly different economic models of store format, their different roles, their often more expensive locations as well as, most obviously, the limited space available.

As one supermarket source puts it: “The whole industry seems to think Which? has lost the plot.”

Andrew Opie, director of food and sustainability at the BRC, gave a more diplomatic take on the comparison. “Clearly convenience stores do not have the space to stock the same range as a supermarket, but retailers will maximise all available space to offer maximum value for their local community,” he said.

Leaving aside the soundness of the investigation for a moment, this latest attack is something retailers are going to have to get used to during the cost of living crisis.

For as long as food inflation continues to be an issue, they are going to increasingly become a target for criticism – especially as it reaches record highs.

It’s not just Which? that has become increasingly critical of supermarkets of late.

Today the Food Foundation, which in recent weeks has repeatedly accused retailers of failing to promote the government’s Healthy Start vouchers scheme or provide enough cheap fresh fruit & veg in their aisles, backed the calls from Which?.

It too released a film, a seven-minute documentary on food poverty called ‘They Know We Are Here’, which focuses on the struggle of a Birmingham mother and features a GP taking aim at the junk food culture of local convenience stores.

After the first screening, executive director Anna Taylor called on MPs at a Westminster gathering to urgently intervene. “It must ask supermarkets to explore what they can do to make nutritious food affordable to low-income families,” she said.

In the void of any meaningful government action on food policy, it seems supermarkets are increasingly going to be the ones facing the flak.

Perhaps campaign groups have simply given up on ministers coming up with any answers to issues like food poverty and the obesity crisis – and, for that, no one can blame them.

By comparison, grocery is more responsive. Campaigners will have seen how Jack Monroe influenced supermarkets to do more to offer affordable products, albeit with slightly back-of-a-fag packet calculations on the level of inflation in value ranges.

These calls for retailer action resonate with the public, too. Which? has already gathered nearly 90,000 signatures for its Affordable Food For All campaign, the target of which is retailers, rather than politicians.

A government website famously requires 100,000 signatures to secure a debate in parliament. One wonders what the numbers have to be to get the executive in the supermarket c-suite paying attention, even if the claims are based on less-than-robust calculations.