Online grocery home delivery group Ocado said sales and orders increased in the quarter between December and February, as the company exceeded the 250,000 weekly orders for the first time.

In the 12 weeks to 21 February, the FTSE 250 group posted a 15.3% year-on-year increase in gross sales to £312.4m (€401.5m, $445.3m), while average weekly orders rose 16.9% from the corresponding period in 2015 to £214,000. Meanwhile, retail sales increased 13.8% year-on-year to £286.7m.

However, the average order size in the first quarter fell 2.9% year-on-year to £111.41, the company said. Despite the slight decline in average order size and a challenging trading environment, the retailer remained upbeat about its outlook.

"We believe our focus on customer satisfaction and commitment to improving what we offer to consumers through innovation and our proprietary IP will support further growth," said group chief executive executive Tim Steiner. "Notwithstanding the tough nature of the marketplace, we expect to continue growing ahead of the online grocery market."

Ocado did not offer any updates over its deal with Morrison's. Since 2013, the latter has outsourced logistics for its own online food business to Ocado, but after Morrisons announced a tie-up with online retailer Amazon in February, the two companies were expected to amend their existing partnership.