The world's largest food companies are failing to meet ethical standards, a report from Oxfam suggests.
It compiled a scorecard which rated the "Big 10" drink and grocery brands on seven social and environmental factors.
These ranged from transparency of their supply chains and operations to how they protect women's rights.
The lowest rated company, UK food giant Associated British Foods (ABF), said it treated local producers with the "utmost respect".
Oxfam has launched a Behind the Brand campaign in 12 countries calling on the public to use social media to put pressure on the companies to improve their policies.
The charity said few of ABF's brands were able to demonstrate how they did business with suppliers or enforced ethical standards.
The company scored one mark out of 10 in its treatment of land, women and climate change, while its highest scored was three, on workers and transparency.
In joint second lowest place were Kellogg's and General Mills, which owns Old El Paso, Haagen-Dazs and Nature Valley, both scoring 16 out of 70.
The report said neither ABF and Kellogg's had addressed land rights concerns or the poverty and lack of opportunity for women working in the supply chain.
General Mills showed a lack of transparency in the source of their ingredients, only providing information on where they get their palm oil, Oxfam said.
The company which achieved the highest score was Nestle, with 38 marks.
Oxfam said all 10 companies had acknowledged the need for a more just food system and had made commitments to achieve that, but were still failing to take adequate steps.
It also found that while all of the companies had moved to reduce direct emissions, only five - Mondelez, Danone, Unilever, Coca-Cola and Mars - publicly reported on agricultural emissions associated with their products.
Oxfam chief executive Barbara Stocking said: "Consumers have the right to know how their food has been produced and the impact this has on the world's poorest people who are growing the ingredients. Companies have a responsibility to treat local producers, communities and environments with respect.
"It is time the veil of secrecy shrouding this multi-billion dollar industry was lifted.
"The hundreds of brands lining supermarket shelves are predominantly owned by just 10 huge companies which have combined revenues of more than one billion dollars a day whilst one in eight people go to bed hungry every night."
ABF owns brands including Kingsmill, Twinings and Ryvita.
The company said in a statement that the idea it would use a veil of secrecy to hide the human cost of its supply chain was "simply ridiculous".