Shares in Ocado slid this morning after the online retailer eked out another modest profit for the past six months.

Sales were up 12% to £332.3m, with orders up 13% - offsetting a slight fall in the average basket size. Ocado said it served 337,000 customers in the period, up 19% on the same term last year, while sales from mobile phones were up almost a quarter (24%).

Despite the higher sales, profits came in at just £181,000 for the six months to 13 May – a marginal increase on the £174,000 record last year.

Chief executive Tim Steiner was cautious about the third quarter, warning that the Jubilee celebrations had caused some “disruption” for Ocado. He also warned of “uncertainty” over the impact on sales of the Olympics.

“The last six months has been all about delivering our plans to increase capacity, efficiency and range and enhancing our offer to customers,” Steiner said.

“We continue to put in place the building blocks to deliver further improvements in the rest of this year and future periods.

“Ocado now offers a grocery range which compares favourably against all of the large physical supermarket groups and we have continued to deliver new ideas and innovations to improve our offer to customers.”

But he warned: “The third quarter is particularly hard to forecast as we have already seen some disruption from the Jubilee events and there is uncertainty as to the effect of the forthcoming Olympic Games, but we expect sales growth to increase in the second half overall.”

Meanwhile, Ocado confirmed the appointment of Duncan Tatton-Brown as its new chief financial officer. The former Fitness First CFO comes on board on 1 September as a permanent replacement for Andrew Bracey.