Almost one in five products sold for a “round pound” in an Asda campaign are more expensive than they were five months ago, research has revealed.

A total of 173 out of 969 products (18%) were found to be more expensive in July than in March, with the supermarket apparently rounding up rather than down, trade magazine The Grocer found.

The magazine checked the prices of round pound items found recently on the Asda website against prices offered on March 1.

Of the 969 products it looked at, it found 477 items were cheaper in July than March, 319 were exactly the same and 173 were actually more expensive, with 46 of these previously on sale at 90p or less.

The Grocer said: “Asda's heavily publicised round pound lines have become a key part of its promotional offer — but almost one in five of these lines sold for less than a quid just months ago.”

The Asda campaign, launched at the beginning of the year, promises 7,000 items at one pound or less.

An Asda spokesman said: “Our commitment to customers is clear — we will always have 7,000 different products priced at £1 or less.

“While those products might change, the value we offer remains the same”