Technical problems have marred the launch of Nectar, the new customer loyalty reward card scheme run jointly by J Sainsbury, Debenhams, Barclaycard and BP.

Customers hoping to sign up to the scheme online on Monday found that the Nectar website was not working properly.

Nectar blamed the glitch on unexpectedly high levels of demand, and said it had upgraded the website to enable it to cope with greater numbers of users.

"The sheer number of people trying to access the site meant that there were temporary problems," a spokeswoman told BBC News Online.

"We're not the first website to have problems on the launch date, and we hope people will try again."

Points swap

Nectar allows its sponsors' customers to collect loyalty points which can then be redeemed for flights, holidays, meals and cinema tickets.

It is modelled on the Air Miles loyalty programme, which allows shoppers to swap points for free air travel.

Nectar's launch comes amid growing doubts over whether customer loyalty schemes help to attract new business.

Two years ago Safeway cancelled the loyalty card scheme in all its supermarkets, arguing that customers prefer immediate discounts at the till to points on a card.

Quick reward

But 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.

J Sainsbury surrendered its place on the Air Miles scheme to rival Tesco earlier this year.

Tesco claimed on Tuesday that the Air Miles programme had helped it attract 60,000 new customers over the last six months.