Supermarkets are failing to get some basic products such as milk, bread and butter on the shelves, a study by the Grocer magazine suggests.
Mystery shoppers found empty spaces on shelves
The Grocer tested the availability of 33 basic goods and found twice as many were out of stock as six months ago.
Analysts said that supermarkets "had taken their eye off the ball" and were focusing more on reducing waste and packaging than getting items in stock.
Tesco said availability was high and queried The Grocer's study methods.
The Grocer used mystery shoppers to check price and availability of 33 items - picked to reflect an average consumer's shopping basket - in different branches each week.
Six supermarket groups were tested: Tesco, Sainsbury's, Asda, Morrisons, Waitrose and Somerfield.
During the 26 weeks from 17 June to 9 December Somerfield recorded 48 occasions when one of the 33 items was out of stock.
This was the worst performance of the six major supermarkets groups tested.
Sainsbury's, Waitrose and Tesco performed very similarly to one another; while the best two supermarkets for availability were Asda and Morrisons.
But overall, the number of items out of stock was much higher than for the previous six-month period.
According to Gaelle Walker, reporter for the Grocer, supermarkets were failing in "basic shop keeping".
"The number of out of stock items has doubled in all the supermarkets... there seems to be a bit of a problem here.
"Analysts I spoke to believe the supermarkets have taken their eye of the ball; become distracted by side issues such as reducing waste and packaging," she said.
But a spokesman for Tesco, the UK's biggest supermarket chain, told BBC News that there was no link between reducing waste and availability.
"I fail to see how environmental measures have any effect whatsoever.
"What I do know is that the Grocer sample of 33 products is small and that it only takes one store to be down on the items, because say of a rush or seasonal factors, to skew the figures.
"We have our own, very-sophisticated stock control measurements and availability is much better than the picture painted by the Grocer study."