'Six eggs used to be £1' - why everyday essentials cost so much more now

AJ Bell head of financial analysis Danni Hewson says contracts between producers and supermarkets are signed in advance.

"Without a crystal ball nobody can know what is going to happen" to producers' and farmers' costs at the moment these contracts are signed.

While that means farmers can ask for more money when a contract is up for renewal, that can't usually occur mid-contract when energy or fuel prices skyrocket.

"So there will be a degree of some of these price increases, obviously, having to be swallowed by some of these producers," she says.

A loaf of basic medium slice white bread cost 65p in 2022 but that's now risen to 74p on average in the big supermarkets. Assosia does not have data for discounters like Aldi and Lidl but the other supermarkets tend to price match as competition for customers is so fierce.

The increase in the cost of wheat after Russia's invasion of Ukraine which led to rising bread prices has levelled out. However conflict in the Middle East has sparked global supply fears, according to The Andersons Centre.

Hewson said there has been a "perfect storm" of increased costs for raw materials, energy, labour costs and even changes to packaging regulation that has made these essentials more expensive.

It can be galling that while the total at the checkout continues to rise, supermarkets are seemingly profiting.

Sales at the UK's main supermarkets rose from about £130bn to about £160bn between 2020 and 2024.

But when we take their sales and operating expenses into account, none of the main retailers' profit margins have increased over the last 20 years.

While these figures don't drill down into how much of those sales were for food, and they can't reveal how much profit was made on fresh fruit, meat or dairy products, experts say they do illustrate how competitive the supermarket industry is in the UK.

The Competition and Markets Authority's July 2024 investigation into the groceries sector found no evidence that supermarkets were artificially inflating prices.

There was no spike in 2022 and 2023 when food prices soared as a result of the global energy crisis following Russia's invasion of Ukraine.

Hewson says the UK supermarket sector is "massively competitive", and most will sell some staple products at a loss to get people through the door.

"In most of those cases, what happens is the supermarket swallows those losses. And that impacts their margins," she says.

"These are not businesses that are making huge amounts for every pound that they sell. They have to work hard to make their money."

Andrew Opie, director of food and sustainability at the British Retail Consortium, which represents supermarkets says the UK was "one of the most affordable places in Western Europe for grocery shopping".

"As food inflation has risen in recent years, supermarkets have ramped up their focus on offering value on everyday staples - in some cases selling products below cost and absorbing the impact through their own margins to deliver savings for customers," he added.