Hundreds of supermarket items have shrunk in size while their price has been kept the same or even increased, the consumer group Which? has warned.

In its latest round-up of shrinking groceries, Which? found that toilet rolls, chocolate biscuits and orange juice were among the popular shopping items that had had a de facto price increase.

Which? researchers found that Andrex had cut the number of sheets on its standard toilet rolls from 240 to 221 sheets – an 8% fall. The price had remained roughly £2 for four rolls, the watchdog found.

Those who enjoy a McVitie’s dark chocolate digestive biscuit are also set to be disappointed. Which? found the packet had decreased from 332g to 300g, a reduction of more than 10%. These had sold in Tesco for £1.59 before the packet size shrank, but had increased to £1.69 afterwards, it said.

Tropicana Creations Pure Premium orange and raspberry juice decreased from 1 litre to 850ml, a 15% reduction, yet it had remained at £2.48 in Asda.

Which? said the latest cuts were only the latest in a series. Since the credit crisis hit wages hard, retailers and manufacturers have increasingly turned to shrinking products as a way of pushing through a price increase in the hope that consumers will not notice.

In some cases, the obesity crisis has been used as a reason to cut the size of high sugar and fat items, but some observers suggest it is more to do with profits.

Last year, Cadbury’s angered its loyal customers when it cut the size of Creme Eggs and took two biscuits out of boxes of Fingers. When John West shrank its No Drain tuna steak in brine from 130g to 120g, the price stayed at £1 in Morrisons. And there was no change in the £5 cost of Surf with Essential Oils washing powder when it dropped from 2kg to 1.61kg.

Which? editor Richard Headland said: “Shrinking products can be a sneaky way of increasing prices. We want manufacturers and supermarkets to be upfront so consumers aren’t misled.”

Headland said brands that responded to the Which? research countered that it was up to supermarkets to set prices, but they would not disclose if they had charged the stores a lower wholesale price.

A poll by Which? found 78% of its members did not think it was right if consumers were not told when products dropped in size but remained at the original price.

The latest research found that it is not only food items that were being shrunk. Dettol Power and Pure bathroom wipes decreased from 36 to 32 wipes a packet, an 11% reduction, but remained at £2 in Tesco.

Percol Fairtrade Guatemalan coffee has decreased from 227g to 200g, a 12% reduction and, although the price dropped from £3.90 in Sainsbury’s and Waitrose to £3.65 and £3.75 respectively, it still amounted to an increase per 100g.