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Sainsbury's, which has announced its first sales decline in nine years, plans to launch its new customer website in April.

Its online groceries business is also growing at a slower rate than at the start of the year - when it reported a growth of more than 10% in online groceries sales - while the new website is being implemented. It began gradually rolling out the enhanced online groceries website in September.

"Our groceries online business is growing at 6% year-on-year, reflecting a reduction in marketing while the new customer website is launched. This rollout is now 80% complete and is due to finish in April," Sainsbury's said in its fourth quarter trading statement today.

The supermarket also said that while it expects the outlook for customers to continue to be challenging, it expects to beat its rivals, aided by data from its Nectar loyalty programme.

It said: "We remain confident that our differentiated offer, supported by 'value for values', Nectar data and Brand Match, will allow us to outperform our peers in the year ahead."

Sainsbury's new IT director, John Rudoe, recently revealed how valuable the Nectar loyalty programme, and data gathered by it, is to the company, giving the supermarket insight into its customers and an overview of its omni-channel transactions.

Sainsbury's reported a 1.5% fall in total sales for the fourth quarter, with like-for-like sales declining 3.8% in the period.

However, it has maintained its market share at 17%, according to the Kantar Worldpanel Market Share 12 weeks ending March 2, 2014.