Headlines claiming food inflation is at a 17-year high are wildly exaggerated, with exclusive data from The Grocer revealing prices are up just 3% on last year.

The Daily Mail, Daily Telegraph and Daily Express were among the nationals using figures from price comparison website mySupermarket.co.uk, which claimed soaring costs had led to an 11% year-on-year hike in the average price of a shopping basket.

However, our own data, compiled by market research house ESA since 2004, suggests price rises are not as excessive as press reports claim. In the four weeks to 8 April, the average cost of 150 grocery items across the big four and Waitrose increased by a significantly lower 3.09% compared with last year.

Unlike The Grocer data, mySupermarket.co.uk results did not include prices from Morrisons, whose aggressive price cuts have helped steady food inflation across the retailers over March, as the website extracts pricing information from online shopping websites. But this does not explain the considerable price discrepancy on both the average shopping basket and leading commodity-based products.

The website found a 500g pack of minced beef had increased by 64% over the year. Our data found the same product was only 6% pricier at Morrisons and 9% more at Asda, Sainsbury's and Tesco. Waitrose actually reduced its price by 15%.

Cost pressures on dairy and bakery goods led to a 62% average increase for butter, claimed mySuper­market.co.uk, with a French baguette 33% dearer than a year ago. But, these figures are 10 percentage points too steep, according to our data, with butter 52% higher and a French baguette 23% more.

Other discrepancies include the price of a 250g block of mild Cheddar, which rose 17% across the retailers according to our survey - not 26% as recorded by the website. This average was driven down by Sainsbury's, which is selling the cheese for 7% less than it did 12 months ago.

Sainsbury's prices for the 150 items went up the least - just 1.3% - compared with 2.8% at Morrisons, 3% at Tesco, 3.7% at Waitrose and 4.4% at Asda.

"We have a responsibility to deliver the best products at the most competitive prices," said a Sainsbury's spokeswoman. "The Grocer's latest price inflation figures show that we are finding real success in keeping prices as low as possible for our customers."

Tesco said it was disappointed with the press reaction, which came a week after The Grocer exclusively revealed that retailers had stabilised food inflation (Retailers put a lid on it, The Grocer, 12 April, p4).

"Despite scaremongering among some quarters of the press this week, it is good that people are recognising what an important role supermarkets and competition play in keeping a lid on inflation," said a Tesco spokesman. "Data will always be more accurate when it is collated from a broad basket of goods, especially when it is not weighted toward any particular product category," he added.