Consumer power is forcing British supermarkets to insist on better conditions for Third World workers, the international charity Christian Aid reported this month.

A church in London collected 45,000 pounds sterling ($73,000) of cash register receipts and handed them back to local supermarkets. This was just one of the churches and groups which responded to Christian Aid's call to collect till receipts to show how many people in Britain are concerned about the working conditions of people around the world who produce the food they buy. The message, says Christian Aid in its report - Change at the Check-out? - is clear: "If the supermarkets want consumer loyalty, they must show loyalty to the people who produce our food on the other side of the world."

Christian Aid, which is backed by most mainstream churches in the UK and Ireland (with the exception of the Roman Catholic Church), combines an extensive programme of grants in over 80 countries with vigorous campaigning on issues like Third World debt, unfair trade practices and reform of the World Bank and the International Monetary Fund. A year ago Christian Aid launched a campaign to persuade British supermarket chains - the top 10 supermarket chains had a turnover of 53 billion pounds (US$86 billion) in 1996 - to use their economic clout to improve material conditions and ethical standards for food workers in the Third World.

It had uncovered many shameful cases: Peruvian asparagus-pickers receiving the equivalent of 2 US cents out of the $9.83 per kilo paid by the consumer; Brazilian grape-pickers suffering from pesticide-linked illnesses while getting less than 4 cents per lb (0.45 kg) although consumers pay $2.13; Sri Lankan tea workers receiving only 7 per cent of the price paid by the consumer. After a year of campaigning, Christian Aid has found that seven of the top 10 British supermarket chains, including the biggest, Tesco, have adopted ethical sourcing policies. Six are drawing up codes of conduct and have agreed to external verification. Change at the Check-out? warns that without further steps, "codes of conduct will become little more than a PR [public relations] exercise, fancy words for business as usual". Michael Taylor, director of Christian Aid, said: "We want people to be able to walk off the street into any supermarket and buy their food, confident that it has been produced without exploitation." Britain's top 10 chains were asked 12 questions about their ethical trading policies, and the answers were evaluated by independent specialists including Richard Harries, the (Anglican) Bishop of Oxford. The biggest surprise was that the clothing and food group Marks & Spencer, seen in Britain as a byword for fair trading and high standards, was one of three companies that did not answer the questionnaire. However, Marks & Spencer told Christian Aid of "the care we take in our approach to the procurement of St Michael [its own brand label] merchandise, in particular the work we have been doing with our supply base in achieving high standards of staff welfare and rewards". The highest-ranking supermarkets in terms of ethical trading were the two biggest chains, Tesco and Sainsbury's, together with fourth-biggest, Safeway. In order to improve conditions for Third World workers, Christian Aid says it places freedom of association - the right to join a trade union - at the top of priorities for its model code of conduct for suppliers to British supermarkets.