One in four bananas sold in Sainsbury is now Fairtrade, according to the retailer, and sales of Fairtrade bananas are growing faster than non-Fairtrade at a rate of 27% year on year compared with 10% for conventional fruit.

Sainsbury has just moved its children's bananas to Fairtrade fruit with the introduction of Fairtrade kids' bags but at the same 99p-a-bag price, saying that the grower would receive more.

It has also introduced loose Fairtrade bananas in a trial in 54 stores.

Sainsbury also claims that its customers buy the most Fairtrade bananas of any retailer, and that it sells more than a third of all Fairtrade bananas sold in the UK.