The M&S and Oxfam Clothes Exchange is designed to raise money for Oxfam and to reduce the one million tonnes of clothing sent to landfill sites in the UK each year.
Customers who donate old M&S clothes to Oxfam will receive a £5 M&S voucher, valid for one month, to use against purchases of £35 or more at M&S. The exchange will be trialled for six months from January 28 at Oxfam's 790 stores across the UK and Republic of Ireland.
M&S chief executive Stuart Rose said: "We are pleased that we have teamed up with Oxfam, the UK's biggest charity shop, to help customers raise money for developing countries by recycling their clothes. It's a triple win - it's good for customers, good for people in developing countries and good for the environment."