An ASA spokeswoman confirmed that the body was studying the case after its preliminary assessment found the complaint was worth investigating.
Tesco complained directly to Ocado two months ago after it ran press ads claiming to match Tesco on 3,500 branded products, including Coca-Cola and Pampers.
A Tesco spokesman described Ocado's campaign as "underhanded and misleading".
The supermarket has told the ASA that its Waitrose-linked rival in home shopping is regularly more expensive on at least 500 items.
Jason Gissing, the marketing and finance director at Ocado, told The Times: "We are not surprised that Tesco have decided to act with their customary aggression but we are disappointed they don't have more important issues to focus on.
"They have clearly realised that their initial response of price-cutting goods we both sell has not worked."