After 16 November 2002 they will no longer be able to collect reward points on their Sainsbury's Reward cards, but must use the new Nectar loyalty card instead.

Unless their existing reward points are converted into Nectar points, they will also have to redeem their Reward points by January 2003.

Nectar is the new customer loyalty reward card scheme run jointly by J Sainsbury, Debenhams, Barclaycard and BP.

Net registration woes

Nectar's sponsors say their scheme will allow customers to tally up points more quickly than with other cards.

They hope to persuade 50% of the UK's households to sign up, making Nectar the country's biggest customer loyalty programme.

The points are exchangeable for a range of goods and services including shopping, flights, holidays, meals and cinema tickets.

The scheme's launch in September attracted some negative publicity after its online registration system failed.

There are still technical difficulties with the site, and potential customers can still not register online.

Instead, they are being encouraged to send in their application by post.