Waitrose.com sales increased 55% year on year for the week ending 18 August.
Ocado is now competing directly with Waitrose in the capital after an agreement between the two brands that restricted Waitrose from making deliveries within the M25 came to an end last July. The pair still have a partnership allowing Ocade to sell Waitrose products.
However, Ocado founder Jason Gissing claimed last May that there was enough space for everyone in the market and said only 20% of its products were from Waitrose.
Ocado is aggressively attempting to combat increasing competition from the likes of Waitrose and Tesco and has appointed BD Network to create an autumn ad campaign stressing its product quality, service and difference to established supermarkets.
Meanwhile, Ocado founder Tim Steiner recently announced plans to launch a price war in the online grocery market to convince customers it is the cheaper option.
Waitrose claimed the online delivery boom was the driving force behind a 10.2% overall sales increase for the week ending 18 August.
Recent Kantar Worldpanel market share data for the 12 weeks ending 5 August shows Waitrose is out-performing the market with growth accelerating at 7.4%, which is almost double the total grocery market growth rate of 3.9%.