Sainsbury’s claimed it has overtaken Asda to become the second- largest seller of online groceries, behind Tesco.

Sainsbury’s said it has seen a 20% rise in weekly average orders in the past year to 165,000 and has generated revenue of £750m in the past 12 months. Market leader Tesco expects to double its online grocery revenue to £5.5bn in the next five years.

Sainsbury’s online director Jon Rudoe said: “We’ve got ambitious growth targets which we’ll reach by continuing to deliver the best possible experience for our loyal and new customers.”

However, Ocado has questioned the validity of further claims made by Sainsbury’s. JS said an Ipsos Mori shopper survey showed it to be the best operator in terms of quality, service and delivery.

The survey showed Sainsbury’s came out on top in several key areas with Ocado coming last in four out of five categories. Almost 1,000 Sainsbury’s shoppers, 400 Tesco shoppers, 400 Asda shoppers and 200 Ocado shoppers were surveyed. Ocado argued the sample was unfair.

Chief executive Tim Steiner said: “There is a high correlation between the sample size and the positioning in the survey which says it all.”

Kantar Retail director of retail insights Bryan Roberts said competition will be intense in online grocery. He said: “In the US, Amazon’s Subscribe & Save scheme has worked well and Ocado have followed suit with its Savers Pass.

I suspect we’ll see more retailers looking to embed incentives for long-term loyalty.

“An increasing number of suppliers are dedicating account managers to Amazon for a lot of large, bulky ambient products.”