The BBC's John Moylan: "Loyalty cards do not deliver loyalty"

The study by market research company Mintel found that the number of people with loyalty cards has not increased in the past two years.

Asda has high customer loyalty but no card

Their research also found a third of people preferred low prices to points or other incentives.

Loyalty cards were first launched in the UK by the supermarket chain Tesco.

The supermarket brought out their card in 1995 to encourage shoppers to return to their stores to build up points which would lead to discounts on certain items.

Most major retailers copied the idea, and by 1997 75% of all adults had signed up to at least one loyalty scheme.

But the study found there was mixed evidence that the cards really promote loyalty.

The supermarket chains Morrison's and Asda have a higher than average proportion of shoppers describing themselves as loyal - but they do not run such schemes.