Poor pay and harsh working conditions are common on foreign farms and plantations that supply tea or fruit to UK supermarkets including Lidl, Aldi, Sainsbury’s, Tesco and Morrisons, according to an Oxfam report.

The charity claims that a “relentless” drive by supermarkets to cut costs and maximise profits is fuelling poverty, abuse and gender discrimination in their supply chains originating in India and Brazil.

It said interviews with workers on 50 tea plantations in Assam in India revealed that cholera and typhoid were prevalent because workers lacked access to toilets and safe drinking water.

It found that half the workers questioned received ration cards from the government because wages were so low, while female employees regularly worked for up to 13 “back-breaking” hours a day.

Oxfam said Aldi, Morrisons, Tesco and Sainsbury’s had confirmed that they sourced their own-brand tea from companies whose suppliers included the estates visited by the charity.

Oxfam also found that, of the 79p paid by shoppers for a 100g pack of black Assam tea in the UK, supermarkets and tea brands receive 49p while workers collectively received 3p.

The charity said workers on the Assam estates could earn a living wage if they were paid just 5p more of the retail price.

On fruit farms in north-east Brazil, women with children reported having to rely on relatives or government support to feed their families outside the harvest season.

Workers also reported developing allergies and skin diseases as a result of using pesticides and other chemicals without adequate protection on grape, melon and mango farms that supply supermarkets including Lidl and Sainsbury’s and previously Tesco and Morrisons.

Oxfam ethical trade manager Rachel Wilshaw said: “Despite some pockets of good practice, supermarkets’ relentless pursuit of profits continues to fuel poverty and human rights abuses in their supply chains.

“Supermarkets must do more to end exploitation, pay all their workers a living wage, ensure women get a fair deal, and be more transparent about where they source their products.”

She added: “Supermarkets are snapping up the lion’s share of the price we pay at the till but the workers who toil for hours to harvest tea and fruit face inhumane working conditions and are paid so little they can’t even feed their families.”

British Retail Consortium head of sustainability Peter Andrews said: “Supermarkets in the UK are spearheading actions aimed at improving the lives of the millions of people across the globe who contribute to the retail supply chain.

“Our members are working hard to address existing injustices and continue to collaborate internationally with charities and business groups on this vital issue.”

A Tesco spokesman said: “This is the second year in a row that Tesco has been assessed by Oxfam as doing most, of all major supermarkets globally, to ensure human rights are respected in food supply chains.

“All our tea is 100% Rainforest Alliance certified and we are a member of the Ethical Tea Partnership, committed to improving the lives of tea workers and ensuring minimum working conditions.

“But we know there is always more to do and we are working collaboratively with NGOs, trade unions and others to improve wages in the key produce, tea and clothing sectors and ensure working conditions are fair.”

Aldi said: “We continue to work hard to ensure every person working in our supply chain is treated fairly and has their human rights respected. We share the values behind Oxfam’s campaign and are in regular dialogue with them.”