Users have complained the site is slow and difficult to navigate following its relaunch in March. In a statement issued this week, director of e-commerce Robin Phillips said increasing the speed of the site was a "top priority" and that its focus over the past couple of months had been "an initial phase of fixes" for "the overall speed of the website, the management of shopping lists and previous orders, and the ease of the checkout process".
The next phase of improvements including speed, usability, content and accessibility is due to go live in early July.
This apology comes three months after the company's last, released on its Facebook page. Users blasted Waitrose, complaining "loyalty had been squandered" and vowing to switch to Ocado and Tesco.
Waitrose expanded its online operation within the M25 this week, putting it in competition with Ocado.