A long-running voucher scheme run by British retailing giant Tesco was slammed by the Consumers' Association (CA) today [Thursday] in a report that also singles out the Walker's Crisps' Books for Schools promotion as encouraging unhealthy eating.

In its Which? magazine, the CA argues that parents and schools are led to have unrealistic expectations of how much computer and reading equipment will be generated by their saving up vouchers given when they spend a certain amount of money in-store.

Jenni Conti, lead researcher, explained that parents would have to spend nearly £250,000 (US$355,000)a year in Tesco in order to generate enough vouchers to provide a school with a computer worth £1,000. "There is also little consensus among the main teaching unions and parent-teacher bodies as to whether schemes are a good idea," she added.

Tim Mason, marketing director at Tesco, was stunned by the criticism. He told the Guardian:  The criticism from the Consumers' Association is astonishing, and flies in the face of the praise the scheme has received from the prime minister, the education secretary, and thousands of parents and teachers around the country.

"It is extremely popular with millions of Tesco customers," he added, "which is why it has been running ten years and helped schools receive £70m worth of equipment." This year it provided 22,000 schools with 70,000 items, of which 4,000 were computers.

The promotion was highly criticised at one point however for providing extra vouchers on snack food products and fizzy drinks; popular with children but unhealthy. The Walkers/News International Books for Schools promotion was slammed for that reason, as health officials raised concerns that children would up their intake of crisps.

A spokeswoman for Walkers maintained however: "We are immensely proud of the initiative and the benefit it has brought to more than 30,000 schools all over the country.

"During the three years of the scheme with News International, we have given away over 6m books worth over £33m."