Ocado has vowed to continue advertising its pledge to match Tesco prices on branded products, despite a ruling by the Advertising Standards Authority (ASA) that two adverts published last year breached its code.

The price match claim could not be substantiated because of Ocado's method of gathering the prices from Tesco's website, the ASA ruled.

Since the complaint was made by Tesco, Ocado had switched to a "new, fully reliable system", a spokesman said. The technical problem, which involved the 'scraping' of Tesco's website for prices, was "something we addressed a long while ago", he added.

Obsolete barcodes on hundreds of products on the Tesco website had meant Ocado was unable to match all of the latest prices. But the technology had since been improved to pick up and register the out-of-date barcodes, Ocado said.

Tesco, however, continued to dispute Ocado's price match claim. "Ocado still fails to match us on hundreds of products and we believe they should focus on helping their customers spend less rather than trying to pull the wool over their eyes with smart advertising gimmicks," a spokesman said. "We're pleased the advertising regulator agreed that Ocado had misled customers with false price matching claims that they could not substantiate ."

In the initial complaint, Tesco had said Ocado's weekly price check meant the price match claim was often out-of-date. In the ASA's ruling, it noted that following Ocado's weekly 'scrape' of Tesco's website, "Tesco could change their prices during the course of the day for some products, rendering Ocado's price match claim inaccurate. We noted this could apply to a large number of goods and were concerned there was potential for consumers to be misled."

However, the ASA said most consumers would consider a weekly update acceptable and confirmed that Ocado's plan to publish the exact time the price match was made would clarify the policy further.