Oxfam has partnered with Co-op food stores to enable shoppers to donate money to the charity at checkouts throughout the UK.
Customers can purchase barcoded Oxfam Easy Giving Vouchers for up to £2, which will then be scanned along with grocery purchases. The amount will automatically be added to their final shopping bill.
More than 1,300 Co-op food stores will sell and accept the vouchers, which have been designed to offer a quick and easy way to donate money to charity.
"We believe the simplicity of adding one of the vouchers to your shopping basket will appeal to many people who would like to give more often to charity," said Simon Collings, director of fundraising at Oxfam. "We've made it clear that every penny will be used by Oxfam on clean water projects and make a difference to people's lives," he said.
The first project will fund the provision of a well for clean drinking water in Eritrea, East Africa.