More than 2,500 products have shrunk in size over the past five years, but are being sold for the same price, official new figures show.
It is not just chocolate bars that are affected by the so-called “shrinkflation” phenomenon, according to the Office for National Statistics (ONS).
Toilet rolls, coffee and fruit juice are among the 2,529 goods that are also getting smaller without getting any cheaper.
While the move has had little impact on the headline rate of inflation, the change in packet size has contributed 1.22 percentage points to the rate of inflation for products such as sugar, jam, syrups, chocolate and confectionary.
The ONS said most manufacturers blamed the need to resize their products on rising raw material costs.
But the European import price of sugar sank to its lowest level on record in March this year, while cocoa prices have dropped sharply since the record highs seen in 2015, the ONS said.
In November 2016, Mondelez, the maker of the iconic triangular bar Toblerone, said it had increased the spacing between the distinctive chunks and reduced its weight by almost 10% due to rising ingredient costs.
The same month, Mars too pointed to rising costs for its decision to shrink the size of Maltesers packets by 15%.
In recent years the firm has also come under fire for reducing the size of Mars and Snickers bars.
Since Brexit, the pound has tumbled against the US dollar, making imported goods more expensive.
However, the ONS said it had seen no evidence of a Brexit effect on the shrinking size of chocolate bars.
“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.
“But our analysis doesn’t show a noticeable change following the referendum that would point towards a Brexit effect.
“Furthermore, others (including Which?) had been observing these shrinking pack sizes long before the EU referendum, and several manufacturers have denied that this is a major factor.”