All Cadbury chocolate bars sold in multipacks will shrink by the end of 2021 to reduce their calorie count, owner Mondelez has announced.
Popular treats including Crunchie, Twirl and Wispa bars will contain no more than 200 calories each when sold in a four-pack.
However, the price will stay the same. Bars sold individually will not change.
Chocolate fans took to Twitter to denounce the latest example of what has become known as "shrinkflation".
That is when food manufacturers reduce the weight of their products without shrinking the price.
"We must play our part in tackling obesity and are committed to doing so without compromising on consumer choice," said Louise Stigant, UK managing director at Mondelez International.
When asked why "single-serve" bars were unaffected, a spokesperson for Mondelez said the firm believed in "offering consumers different portion sizes for different occasions".
The spokesperson confirmed that the list price for multipacks would not change and said pricing was up to retailers.
'Profit or health?'
Consumers were sceptical, with one tweeting that Cadbury should change the name of its Double Decker bar to Minibus.
They are all at it, the double decker is barely a minibus these days 😂— kev (@splootman) July 17, 2020
"Cadbury trying to say that the change is for health reasons when it seems painfully obvious it's for profit margins," said another disgruntled customer.
“The list price for these products will not be changing at this time”... Cadbury trying to say that the change is for health reasons when it seems painfully obvious it’s for profit margins. https://t.co/XlY5LjAo60— Ian Guffogg (@ianguffogg) July 17, 2020
This is not the first time that Mondelez has run into opposition after altering the size of its chocolate bars.
In 2016, it reduced the weight of its Toblerone bar from 200g to 150g by spacing out its distinctive triangular chunks, but it reversed the change two years later.
"This is a sign of the times." said Mark Jones, food and drink supply chain expert at law firm Gordons.
"You may remember in July 2017, the ONS (Office for National Statistics) confirmed that 2,529 products shrank in size between January 2012 and June 2017, but their price remained the same. The vast majority of the affected products were food and drink.
"Now we are on the brink of another recession, shrinkflation will probably increase again. Only this time, when the producers are caught, they are likely to point to the obesity epidemic as their motivation rather than their margins."