‘Now even smaller’ and ‘All new, worse recipe’: these are the labels you won’t see on food – but you should | Hilary Osborne

“New improved recipe!” “Now with more cheese”. Manufacturers and retailers have long been swift to announce with fanfare some changes to their products, but there are others they would prefer you didn’t notice. Smaller pack sizes and changes in ingredients to reduce the cost of production – both unheralded – confront the consumer, but unless you look closely you might not know. That’s the intention.

There are the packs of butter that have shrunk from 250g to 200g without the change being advertised, catching out bakers in the process; the dwindling pet food pouches that left cat owners wondering why their moggies were miaowing for more; the olive oil spread that goes by the same name despite the headline ingredient being halved.

Across the supermarket shelves are examples of retailers and manufacturers shaving contents and dialling down expensive ingredients and, it seems, hoping we don’t notice. Shrinkflation – where pack sizes are reduced and prices stay the same, or even go up, and skimpflation – where recipes are reformulated and expensive ingredients cut down – are common and as a result people are spending money on items they think they have bought before and then finding they are not the same.

I’ve written about this phenomenon on several occasions over the past year and when I’ve approached manufacturers and retailers for comment they have typically talked about trying to keep their products affordable at a time of rising production costs. Reformulations and quantity reductions have been “difficult decisions”, presented as trying to protect the consumer.

But the way it is typically done doesn’t protect them. Instead, it makes it harder for shoppers to make an informed decision about what they are buying.

It is left to consumers to play spot the difference with the packaging. It can take time to research if a product has really changed. How is a customer standing in a shop supposed to check? Barclaycard and Which? have found that customers suspect some products are getting worse, but unless you collect old tins and boxes how are you supposed to compare the version you were buying last year with the one that’s sitting in your kitchen?

To make matters worse, only part of this is captured by the official inflation figures. The Office for National Statistics (ONS) takes into account pack size changes. So when it says that the cost of butter has fallen, that isn’t because you now get 200g rather than 250g – the price really has gone down.

But skimpflation goes under the official radar. And that may mean rising costs are disguised. For instance, the price of a box of tissues is recorded, but not the fact that they are smaller and you may now need twice as many to blow your nose.

When the UK’s Competition and Markets Authority examined grocery price inflation last year, it raised concerns about consumers’ ability to compare prices if pack sizes are changing. It said that clear and consistent unit pricing – when, for example, a price per gram is displayed – could help with comparisons as the unit price would rise with shrinkflation. However, it acknowledged “it may not be sufficient as [the] consumer generally will not know what the previous unit price was”. On what it referred to as “scrimpflation”, it suggested consumers would vote with their feet if quality was reduced too much.

“Manufacturers are unlikely to advertise any reduction in quality, and so customers will be unaware of the change, unless they detect a noticeable reduction in quality, at which point they may consider switching to an alternative product,” it said – although it did note that this might be harder with pet food than with other products.

Once one big manufacturer moves the others tend to follow. The budget supermarkets, in particular, follow the lead of the rest of the market, so if higher quality ingredients are cut by the biggest name in the sector, you can bet you will see this filter down. And so you have worse products across the board and nowhere to switch to.

Take the olive oil spread for instance: previously, Bertolli’s version contained 21% olive oil and so did the supermarket versions. Now it appears most contain 10% (Asda seems to be the exception). The pack designs may have changed but there is nothing warning you that the contents have and so customers only discover that they’ve bought something different once it’s spread on their toast.

It doesn’t have to be like this. In France, Carrefour put up signs warning customers of examples of shrinkflation and ministers there and in Germany are reportedly considering ways to address the problem. In South Korea, new laws will oblige manufacturers to make it clear when a product size has been reduced.

In the UK, packaging rules insist that information is accurate and consumers are not misled. This means manufacturers have to change the packet when they make any of these changes. So why not force them to highlight the difference when they make that change?

Ideally, they would have to state exactly what had changed, but even just making them use the words “New recipe” or “New pack size” at a certain font size would alert consumers that they are not buying exactly the same thing as last time and prompt them to scrutinise the packaging further. Maybe some will be honest enough to say “New worse recipe” or “Now even smaller”.