Since launching its Price Guarantee in April, Asda has made more price hikes and fewer price cuts than any of its big four rivals, according to data from pricing specialist Brand View.

And the number of exclusively lowest prices offered by the retailer has dropped by 10% since Asda made the pledge, which it described as "firing the final shot" in the supermarket price wars.

Working on behalf of The Grocer, Brand View has tracked the cost of 1,037 key grocery staples and top-selling products in the multiples during the three months beginning 28 April, when Asda announced its price-matching guarantee.

"Our Price Guarantee is our cast iron promise that your basket of shopping will always be cheapest at Asda," said Andy Bond at the time. Since then, Asda has put up 31% of the prices tracked by Brand View. It upped 319 prices and reduced 236 increasing 35% more prices than it cut.

Tesco and Sainsbury's have also increased more prices than they cut over the same period 11% and 13% respectively while Morrisons cut as many prices as it raised.

The price rises do not alter Asda's status as the UK's cheapest retailer, but lend weight to the theory proposed by leading competition expert Professor Morten Hviid at the time the Price Guarantee was launched that it could be "anti-competitive" and lead to price increases. At the time Asda described Hviid's theory as "poppycock".

Commenting on the latest figures, Hviid, from the University of East Anglia's Centre for Competition Policy, said: "Price guarantees offer a protection for companies that want to edge prices up. I would certainly expect supermarket prices to become closer."

Indeed, the increases have brought some of Asda's prices on everyday items in line with its big four rivals. A 5p hike on McVitie's Digestive biscuits at Asda to 83p made the price the same as at Tesco, Morrisons and Sainsbury's.

A bag of sweet chilli Snack a Jacks also increased by 5p to cost 45p. This matched the other three retailers, which had left their prices unchanged over the three months.

A kilo of loose carrots has risen from 67p to cost 76p at Asda the same price as Morrisons and just a penny less than at Tesco and Sainsbury's.

On 28 April Asda offered the lowest price exclusively on 277 items out of the 1,037 Brand View monitors on 28 July that figure had fallen to 249. It matched the prices of its rivals on 651 items in July compared with 634 back in April.

Asda continues to publicise key prices cuts on items such as milk, bread and bananas, which it claims will balance out the cost of its shoppers' bills in light of its commitment not to sell below-cost alcohol.