Amex has taken the opportunity created by Barclaycard's withdrawal from Nectar to offer a better deal than its rival did; four points for every pound spent in a partner store such as J Sainsbury or Debenhams - two points each from Amex and the retailer. Consumers will also be able to earn one point for every £1 spent when they use their Amex Nectar cards elsewhere. Its annual percentage rate (APR) is 12.9 and carries a transfer rate of 5.9 per cent for the life of any balance switched over.

If you're an ex-Barclaycard customer who previously used it to accrue Nectar points, the Amex card could appeal, says Richard Mason from the price- comparison website money-supermarket.com.

However, there are caveats. "Amex cards will have lower acceptance [among retailers] than Mastercard and Visa in the UK," says Sandra Quinn of the Association for Payment Clearing Services. Boots only began accepting Amex cards in its stores in May.

Financial analyst Moneyfacts urges consumers considering the loyalty scheme to see if the rewards will suit their shopping patterns. Its spokeswoman, Samantha Owens, says that non-partner stores will offer fewer Nectar points and that the benefits are more limited than with a regular cashback scheme.

While Nectar points have to be redeemed either in participating stores or via select gifts, cashback can be spent however the card user likes.

Among some of the better cashback deals is Morgan Stanley's offering of 2 per cent on the first £2,000 spent, and then 1 per cent on any amount above this for the first three months, before halving to 0.5 per cent.

One of Amex's other cards, the Amex Blue, is offering 2 per cent cashback for the first three months but this then tumbles to 0.5 per cent for spending up to £2,000 and then 1 per cent on anything over this.

Ms Owens says the new Amex Nectar card's APR of 12.9 for purchases is competitive, compared to the standard 15.9 per cent from Barclaycard.

But while the balance transfer rate is also low at 5.9 per cent, there are still cards such as the Halifax's One Visa offering 0 per cent on balance transfers for 12 months, she adds.