Shopping for your groceries online is a hotly fought over market with Waitrose, Tesco, Asda and Sainsbury's offering a delivered-to-your-door service.

And now Ocado has stepped up its efforts to become a real contender to the four online grocery giants. This week sees its first as a seven days a week delivery service after introducing its Sunday service.

The online retailer now delivers from 7.30am to 3.00pm on Sundays, but Sunday deliveries are currently confined to London and the South East.

An Ocado spokesperson says its first Sunday service has been successful and there are long-term plans to offer Sunday deliveries to all customers.

Ocado has also reported that two per cent of sales are generated from its iPhone application, launched two months ago.