In November 2016, Toblerone chocolate bars reduced in size by about 10%, provoking outrage online.
As many as 2,529 products on sale in United Kingdom shops have reduced in size while prices remained the same between January 2012 and July 2017, it found, compared with 614 products that have increased in size.
The ONS has also disputed the idea that Brexit was a key factor behind the falling size of chocolate bars.
The issue has regularly made headlines over the past year after the decline in the value of the pound following the Brexit vote.
The same month, Mars too pointed to rising costs for its decision to shrink the size of Maltesers packets by 15%. "Government is asking food companies to reduce sugar in foods, including reducing portions, with soft drink manufacturers set to pay a substantial tax on some of their products in the near future". Global cocoa prices since jumping to a five-year high at the start of last year have plunged "sharply" over the past 12 months, the ONS added.
The ONS also dismissed Brexit as a reason for recent shrinkflation, even though it has contributed to an increase in the price of some imported goods.
As you can imagine, people aren't best pleased with this phenomenon hitting some of their favourite products.
"Manufacturers' costs may also be rising because of the recent fall in the value of the pound - leading some commentators to attribute shrinkflation on the UK's decision to leave the European Union", the ONS said. "Food and drink is a relatively small proportion of this measure", the ONS said. "Over the last few years, journalists have found examples of loo roll, coffee, fruit juice, sausages, beer and chips getting smaller without getting any cheaper".
Since 2012, the inflation rate for products such as chocolate was actually 1.22% higher, when the smaller size was taken into account.
The price of cocoa, another major ingredient, reached a five-year high in December 2015, but has fallen sharply over the last year.
"But our analysis doesn't show a noticeable change following the referendum that would point towards a Brexit effect".
In the majority of cases, the changes have a negligible impact on the headline rate of inflation.