Asda is changing the way it picks online grocery orders as it ramps up efforts to take a larger slice of the online market.

The retailer is constructing a warehouse in Leeds that will act as a "virtual store" for its online shopping order picking in surrounding towns.

Described as a "halfway house" between Ocado's fully automated warehouse and picking direct from stores, it will stock the full range of products but be closed to the public.

Asda said it would merchandise the depot, which will open next to its Morley store by July, in a way that would enable staff to pick online orders more efficiently.

Once the depot was open, orders would no longer be picked from its stores in Morley, Pudsey, Killingbeck, Bradford and Huddersfield, it added.

"We expect to be able to double our capacity for home shopping deliveries in the area, as the delivery vans will now have a larger reach of up to one hour's drive," said a spokeswoman. "The number of slots available to customers will also dramatically increase."

Last week, Asda announced ambitions to increase coverage to "not far off 100%" of the UK from its current coverage of 95% in a direct challenge to Tesco, which covers 98% of the UK.

According to TNS, Asda is the fastest-growing online grocery retailer in a market that grew 35% to £2.9bn in the 52 weeks to 22 March.

Tesco, which commands approximately 50% of the online grocery market, has two dotcom stores - in Croydon and Aylesford - open only to staff who pick online orders.