Consumers are being pressed to join a new campaign by the Fairtrade Foundation, which warned farmers and workers would face poverty if the "dysfunctional" market was not tackled.
The price of bananas has almost halved in UK supermarkets over the past 10 years, while production costs have doubled. Small farmers and plantation workers are "collateral damage" in the supermarket price wars, with the poorest people having to work harder because of the "ever-tightening squeeze" on earnings, it was warned.
Michael Gidney, chief executive of the Fairtrade Foundation, described the price war as "aggressive", and said: "We are calling on the Government to investigate this dysfunctional market, because it is unfair.
"A product that is worth billions of pounds in global trade relies on poverty-level income for the people who grow it."
Colombian banana farmer Albeiro Alfonso Cantillo -nicknamed Foncho - who is in the UK to support the campaign, said: "The prices here are too low for us to have a decent quality of life. We don't see real profit from the effort we put in."
Campaigners believe downward pressure on banana prices is leading to job losses and casualisation of labour in many banana-producing countries.
One in three bananas sold in the UK is fairtrade, but the cost has fallen from around 18p each a decade ago to 11p today - half the price of an apple grown in the UK.
Mr Gidney said in a letter to Business Secretary Vince Cable the price of a kilo of loose bananas had fallen from £1.08 in 2002 to 68p.
He added: "The pressure on price means no one in the supply chain - retailers, banana companies or growers - are able to adequately invest in improving the sustainability of the banana industry."