Ocado has upped its revenue guidance for the year into double-digit percentage growth after a sharp rise in customers over the summer months.

The online retailer said revenue rose 15.5% year on year to £658 million for the quarter ending September 1, while average orders per week rose 14.7% to 437,000.

Average selling prices fell by 0.4% across the group, versus roughly 2% grocery inflation in the UK.

But Ocado, run as a joint venture with Marks & Spencer, had more customers as 1.06 million people shopped with the retailer over the period, versus 961,000 in the same period last year.

Hannah Gibson, Ocado Retail’s chief executive, said: “Our strategy remains focused on giving our customers unbeatable choice, unrivalled service and reassuringly good value.

“We’re seeing the momentum of this, with more customers shopping with us more often, getting even better service at better value.”

While revenue was up versus the third quarter last year, it also marked an acceleration from first-half growth of 11%, as orders and volume growth picked up.

Analysts at Bernstein wrote in a note on Thursday that the revenue growth represented a “strong performance” from the retailer.

The growth is also stronger than recent market data from Kantar, which implied growth of 12.9% over the summer months.

However, this still outpaced the wider online grocery market where sales grew by 4.4% compared with a year ago, Kantar said.

Ocado said in July that its first half losses nearly halved, amid better-than-expected earnings for its robotic warehouse arm.

The group reported a £154 million pre-tax loss for the six months to June 2 against losses of £290 million a year ago.