McDonald’s, the fast food giant, is to sign a £1m deal to buy coffee from South and Central American farm co-operatives that have been certified by the fair trade watchdog, the Rainforest Alliance.

According to The Sunday Times, the deal – said to be the UK’s biggest of its kind – will mean that 3,000 farmers in 15 countries will receive £900,000 for 800 tonnes of coffee at market rates and an extra 5.5p for every additional pound sold, with a premium of £100,000 each year.

The firm is spending £500,000 on a radio and poster advertising campaign to promote its new coffee and its new ethical image, using the slogan “our coffee doesn’t cost the earth”.

European McDonald’s outlets will follow the UK’s lead and change to fair trade coffee later this year, in a £50m deal.