Justin King insisted this week that Sainsbury's would remain competitive, despite a prediction that Tesco's growing buyer power would allow it to open a big price gap with its rival.

Analysts at Citigate said it had calculated that Sainsbury's sales would have to grow 20% year-on-year just to maintain the current sales differential with Tesco.

This meant it was inevitable the chasm between the two chains would grow, leading to an even greater imbalance in buying power in Tesco's favour.But buying power did not always lead to better prices, said King, chief executive of Sainsbury's. "I don't buy the scale advantage," he said. "The products you buy, and the margins you make, depend on the way you do business."

The analysis by Citigate comes after we reported last week that The Grocer Price Index of 100 grocery items had gone up 4.6% at Sainsbury's in a month compared with an increase of 1.93% at Tesco. "I am confident this was just a blip," said King. "We audit 11,000 lines each week and this shows our pricing is the sharpest it's ever been. We sell better stuff than the competition, and if our own label lines are slightly more expensive than our competitors' because of the quality, our customers don't mind paying a few pennies more."

King was speaking as Sainsbury's, currently the subject of a £10.6bn takeover bid by Delta Two, reported total sales up 4.7%, excluding fuel, for the 16 weeks to 6 October. Like-for-likes rose 3.1% while like-for-like growth in the first half of the year was 4%, excluding fuel.

King said he wanted to stay on if the takeover succeeded - and he insisted that the resulting highly leveraged finance structure would not hinder the chain in its ability to compete.