Workers making clothes that end up in the stores of the biggest names on the British high street have testified to a shocking regime of abuse, threats and poverty pay. Many workers in Indian factories earn so little that an entire month's wages would not buy a single item they produce.

Physical and verbal abuse is rife, while female workers who fail to meet impossible targets say they are berated, called "dogs and donkeys", and told to "go and die". Many workers who toil long hours in an attempt to support their families on poverty wages claim they are cheated out of their dues by their employers.

The allegations, which will be of concern to household names including Gap, H&M, Next and Walmart, were made at a human rights tribunal in the southern Indian city of Bengaluru. The "national people's tribunal for living wages and decent working conditions for garment workers" was convened to investigate widespread human rights abuses in the garment industry.

Sakamma, a 42-year-old mother-of-two working for Gap supplier Texport in Bengaluru, told the tribunal she earned just 22p an hour and that when she finished at the factory she had to work as a domestic help to top up her wages.

"It hurts us to be paid so little. I have to do this and they sell one piece of clothing for more than I get paid in a month," she said. "We cannot eat nutritious food. We don't have a good life, we live in pain for the rest of our life and die in pain.

"Low wages is the main reason. How much burden can a woman take? Husband, children, house and factory work – can we manage all these with such a meagre salary? So we are caught up in the debt trap. Is there no solution for our problem?"

Like many of the women giving evidence, she said workers faced abuse if they failed to meet quotas. "The targets are too high. They want 150 pieces an hour. When we can't meet the targets, the abuse starts. There is too much pressure; it is like torture. We can't take breaks or drink water or go to the toilet. The supervisors are on our backs all the time," she said. "They call us donkey, owl [a creature associated with evil], dog and insult us … make us stand in front of everyone, tell us to go and die."

According to Indian government figures, the national textile industry is worth £35bn a year and employs 35 million people. Garment exports are worth £21bn. But human rights campaigners accuse international brands of subcontracting to firms paying poverty wages to the people who make their clothes.

A spokesperson for Texport denied setting unachievable targets and said abuse of workers was not tolerated. Gap said: "These allegations describe conduct that violates our Code of Vendor Conduct. We are looking into this matter and will take appropriate action with our vendors, depending on our findings."

The Asia Floor Wage Alliance (AFWA), which organised the tribunal, wants companies to pay a minimum living wage of 12,096 rupees (£138) a month, equivalent to 58p an hour. But the tribunal heard that a factory supplying Gap and Next paid as little as 26p an hour. The supplier – Pearl Global, based in Gurgaon, in Haryana state – admits it has underpaid workers for overtime and has required them to work illegally long hours, but said it had now repaid them. It insists it complies with the legal minimum wage, though evidence submitted to the tribunal by one worker indicated that he was paid below the legal rate.

Pearl Global was first exposed by the Observer for rights abuses in 2010 when it traded as House of Pearl, but it has continued to operate and supply the brands under its new name.

Many workers at the tribunal claimed that long hours and poor health and safety conditions made them ill. One worker said that a colleague was electrocuted by a bare wire last year in a factory supplying Gap. Ashok Kumar Singh, 29, who works for Gap supplier Modelama Exports in Gurgaon, gave evidence that he was paid just 5,097 rupees a month (24.6p an hour), although the legal minimum rate for his job was 5,300 rupees.

He said workers were taught to lie to auditors sent to check up on working conditions. "Before a visit they gather all the workers around and tell them what to say. If we don't say what we are told, we are fired," he said, adding that some workers had been dismissed after complaining to auditors about conditions.

Workers who failed to meet targets were verbally and physically abused, he said. "They call us motherfuckers and push us around and some people get slapped by supervisors and managers," he said. "I feel the companies look at the workers like enemies."

The tribunal, in front of an international jury, took evidence in person from workers and will consider written evidence compiled at regional hearings.

Gap and Next were accused of using suppliers that paid below the minimum legal wage, paid below the legal rate for overtime, and required workers to work excessive and illegal overtime. They also faced allegations, along with H&M and Walmart, of using suppliers that verbally abused staff, while there were allegations of physical abuse against a supplier for Gap, H&M and Walmart.

H&M sent representatives to the tribunal and insisted it was committed to improving working conditions. "The social and environmental responsibility that we take puts H&M's sustainability work ahead of the field in the fashion industry worldwide," said a spokeswoman. "We clearly see these issues as industry problems that need to be addressed at industry level by government, suppliers, trade unions, workers, buyers, etc."

A spokesman for Next said: "Next identified that Pearl Global was falling well short of the group's standard codes of practice in 2010. As a result, Next ceased using this supplier in 2011, after making a determined effort to bring about major change at Pearl Global. Next last reviewed the supplier in July, when the decision to remain disengaged from it was maintained. Next has no plans to recommence manufacturing at Pearl Global."

Anannya Bhattacharjee, international co-ordinator for the AFWA, told the tribunal that despite the recession the garment industry continued to bring in profits. She said workers continued to suffer "shocking, inhuman conditions" and were being paid poverty wages. "Nothing can be more important than a decent living wage for workers working day and night to clothe the world."

• The headline for this article was amended on Sunday 25 November. The woman quoted said workers were treated like "donkeys", not "monkeys".