ONLINE grocer Ocado has delivered double-digit sales growth but saw order sizes take a hit from the enduring supermarket price war.

Retail sales jumped 13.1 per cent to £398.1 million in the 16 weeks to November 27, up from £351.8m over the period last year.

Average order sizes fell 2.9 per cent to £105.61 in the fourth quarter, as it felt the force of "continued industry-wide price deflation" and customers buying fewer goods more often after joining its "Smart Pass" membership service.

Group sales, which includes Ocado's deal to deliver orders for Morrisons.com, also clocked strong growth, rising 14.5 per cent to £436.8 million in the period.

Chief executive Tim Steiner said the firm had taken steps to support its expansion by opening a new distribution centre in Andover, Hampshire.

"The strong growth in sales and order volumes reflects the attractiveness of our retail offer to customers," he added.

Shares in Ocado took a hammering last month after Morrisons unveiled a new one-hour delivery service through Amazon, shifting the competition up another gear in the fiercely competitive grocery sector.

The wider supermarket price war also shows no signs of abating, as the so-called Big Four supermarkets - Tesco, Sainsbury's, Asda and Morrisons - continue to slug it out with German discounters Aldi and Lidl.