Sainsbury's wants to safeguard the future of the "Great British cuppa" and offer a better deal for growers by launching its own brand of ethically-sourced tea.

The supermarket, which has stores in Swindon, plans to re-invest part of the money earned on own-brand tea bags into schemes that will help farmers build their businesses and protect the supply chain.

The pilot project, branded Fairly Traded, will offer farmers a guaranteed minimum price for their crop, as well as a "social premium" to invest in development programmes.

It will also provide access to new markets, and help shield their businesses from global competition, political upheaval and the threat of climate change.

The company said it will start selling boxes of Sainsbury's Fairly Traded Red Label Tea from June.

Group chief executive Mike Coupe said: "The business case is clear.

"Our farmers and growers can expect financial security through long-term relationships and a greater level of support to help them plan for their futures.

"At the same time we safeguard the future quality and availability of the Great British cuppa for our customers."

Sainsbury's will provide a "social premium", an extra charge on the basic price, and set up an advisory board made up of academics, charities, and non-governmental organisations (NGOs) to help devise individual projects for farmers.

The move will coincide with a new sustainability standards programme to establish a social, economic and environmental benchmark for 35 crops and ingredients.

Sainsbury's said it will also appoint an independent chairman to take charge of the advisory board, while also employing a big four auditor to oversee the support programme and its funding.

Mr Coupe added: "As our farmers and communities face mounting challenges, we want to advance the way we work with them over the long-term so that we can secure their businesses, providing them and their communities with a better quality of life and in so doing secure the future supply of great products our customers love for many years to come."