Despite inflation hitting its highest rate in 17 months in April, sparking concerns that a sharp hike in food costs would follow, the market remained relatively stable in May.

According to The Grocer Price Index, average prices in our latest basket of 1,000 items have changed little over the four weeks to 25 May compared with April, up just 0.07%.

Our list of products, which covers all major grocery categories, saw prices for Tesco and Sainsbury's fall 1.2% and 0.7% respectively. Asda's prices hardly budged, falling only 0.1%, but the retailer remained the cheapest on average price across all categories.

Morrisons' prices went up 1.5% over the four-week period, with the most dramatic rises in the chilled category, up 7.2%, and frozen, up 4.1%. However, deli prices fell by a huge 9% the biggest fall in any of the categories at Morrisons.

Despite the rocketing price of oranges and revelations that low Jersey Royal potato crop yields would hinder promotion, prices in the fruit and vegetable category dropped for the first time in two months.

This was largely due to the transition this month from international crops to domestic. When this happens, import costs fall and there are higher volumes of home-grown fruit and veg available, pushing prices down.

Aggressive price wars have also had an impact. As The Grocer reported, last week Tesco was selling whole pineapples at 50p each and Asda and Morrisons were selling them at £1.

Overall, however, prices have only changed fairly marginally, no category seeing more than a 1% increase or decline in prices.

On average across the big four prices dropped 0.8% in both household and fruit & veg and 0.7% in deli products. The most dramatic increases came in the baby sector, which saw prices increase 0.9%.

Other products such as dairy, bakery, chilled and grocery remained fairly stable. The price of alcohol also stabilised this month, suggesting that the price of wines and spirits have increased to compensate for the deep discounts starting to be implemented across the beer category.

Soft drinks continued to rise in price but at significantly less than last month's 1.8%.