The consumer champion has been recording the annual inflation of tens of thousands of food and drink products across three months at the eight major supermarkets.

It also found trust in the sector is plummeting amid the cost of living crisis.

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In December, food and drink inflation was at 15% overall across the retailers - but butter and spreads were up almost double, at 29.4%.

Milk (26.3%), cheese (22.3%), bakery items (19.5%), water (18.6%), and savoury pies, pastries, and quiches (18.5%) also saw higher-than-average price increases.

Which? looked at the some of worst examples in these categories for the three months to the end of December 2022.

It found Utterly Butterly (500g) saw dramatic price rises at several supermarkets including Waitrose where it went from £1 to £1.95 (95%).

Waitrose Duchy Organic Homogenised Semi-Skimmed Milk (one pint) went from 65p to £1.22 (87.1%) - and at Tesco, Creamfields French Brie 200g went from 79p to £1.43 (81.5%).

The worst individual price hike on a food item across all the supermarkets was Quaker Oat So Simple Simply Apple (8x33g) at Asda which went from £1 on average in December 2021 to an average £2.88 in December 2022 - a sharp increase of 188%.

Tesco said: "With household budgets under increasing pressure we are absolutely committed to helping our customers, by keeping a laser focus on the cost of the weekly shop. Earlier this week, we were pleased to be recognised by The Grocer as the retailer doing the most to keep prices down right now.

"So whether it's price matching Aldi on the basics, locking the price of more than a thousand household staples until Easter 2023, or offering exclusive deals and rewards through thousands of Clubcard Prices - we're more committed than ever to providing our customers with great value."

A spokesperson for Asda added: "We're focused on keeping prices on branded and own-label products in check to ensure that Asda remains the lowest-priced traditional supermarket as shown by independent research carried out by Which? Magazine."

Waitrose has been approached for comment.

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Lidl's prices increase the most

Across supermarket ranges, budget (20.3%) and own-brand (18.5%) items were again subject to higher rates of inflation than premium (12.6%) and branded counterparts (12.5%).

Despite being the cheapest supermarket overall according to Which? monthly price analysis, Lidl prices went up the most (21.1%) in December, followed closely by Aldi (20.8%).

An Aldi spokesperson said: "We are the lowest-priced supermarket in Britain. Our customers will always pay less for their shop with Aldi and that is why Which? has named us as the cheapest supermarket in 2022. Value is the number one consideration for most households and our promise to our customers is that we will always provide the lowest grocery prices in Britain."

Lidl was contacted for comment.

Asda had the third-highest inflation but was closer to the average of 15% (15.4%).

Meanwhile, the rate of inflation was slightly lower than average at Waitrose (14.5%), Sainsbury's (13.7%), Tesco (13.1%), Morrisons (12.9%), and Ocado (10.5%).

Trust in supermarkets down

While the industry has traditionally enjoyed a high level of trust from consumers - particularly during the pandemic - Which?'s latest Consumer Insight survey data shows these price hikes have coincided with a drop in trust.

Trust at Aldi and Lidl tended to be lower than rivals 18 months ago but has stayed relatively the same during this period meaning it's now higher than average at +48 and +45 respectively.

Waitrose had the lowest level of trust (+29) among all consumers, though trust levels among its customers were much higher.

The cost of food alongside huge supermarket profits was cited as a reason behind this drop in trust.

One participant, a man in his late 30s from the South East, told Which?: "The cost of food from supermarkets is close to unmanageable for many people, including myself.

"Given that large supermarkets make huge profits, I feel they could keep their prices down while we struggle with the cost of living."

A 43-year-old woman from Yorkshire and Humberside claimed supermarkets "don't care about the consumer and charge whatever they can to make as much profit as possible".

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Calls for healthy budget items

Which? is campaigning for all supermarkets to ensure that budget line items that enable a healthy diet are widely available and particularly in areas where people are most in need, make pricing and offers more transparent, and provide targeted promotions to support people that are struggling most with access to affordable food.

Sue Davies, Which? head of food policy, said: "We know food prices have risen exponentially in the last year and our inflation tracker shows the dramatic impact this is having on everyday products at the supermarket.

"Some households are already skipping meals to make ends meet and our findings show trust in supermarkets taking a hit as many people worry they are putting profits before the people suffering during this cost of living crisis."