As many as 2,529 products have shrunk in size over the past five years, but are being sold for the same price, official figures show.
The Office for National Statistics (ONS) said it was not just chocolate bars that have been subject to so-called “shrinkflation”.
It said toilet rolls, coffee and fruit juice were also being sold in smaller packet sizes.
At the same time 614 products had got larger between 2012 and 2017.
The ONS said the phenomenon of shrinkflation had not had an impact on the overall inflation figures. However, in the category of sugar, jam, syrups chocolate and confectionery, the rate of inflation when adjusted for shrinking products was significantly higher.
Since 2012, the inflation rate for products such as chocolate was actually 1.22% higher.