More than 2,500 products have shrunk in size over the past five years while still being being sold for the same price, according to official data.
The Office for National Statistics (ONS) said the feature, called 'shrinkflation', has taken place predominantly among chocolate and sweets, but can also found in products as diverse as loo rolls, coffee, beer and sausages.
Chocolate bar Toblerone cut the size of standard bar by 12% from 170g to 150g last November, leaving large gaps between the peaks and angering chocolate fans.
US maker Mondelez said the move was a bid to cut costs as raw materials such as sugar and cocoa beans – a key ingredient in chocolate – have risen in price on world markets.
In all the ONS said some 2,529 products it monitored in the UK shrank in size between January 2012 and June 2017. Only 614 products had grown larger in the same period.
A range of products have become subject to shrinkflation in recent years, such as Maltesers, Mars and Snickers, with manufacturers citing rising raw material costs.
"No, you're not imagining it," said the ONS, "some of your favourite sweets really are shrinking".
It added: "When we looked at the data from the last five years, we found that lots of the items we recorded had reduced in size or weight – mostly in the 'food and drink' category."
Brexit not to blame
But research has found that fruit drink Tropicana Orange and Raspberry was reduced by 15% from 1 litre to 850ml. Elsewhere, Andrex toilet roll was cut by 8% after its 240-sheet length was reduced to 221 sheets.
The ONS said the price of sugar and cocoa have "fluctuated" over the last five years.
The data body said after hitting a five-year high in the middle of 2014 European sugar prices have fallen. International 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 statistics body did not blame Britain's vote to leave the European Union for exacerbating the trend.
It said: "There has not been a change in trend since the EU referendum – our data shows that shrinkflation has been used in practice consistently across the past five years."