Garment workers making clothes for international brands in Karnataka, a major clothing production hub in India, say their children are going hungry as factories refuse to pay the legal minimum wage in what is claimed to be the biggest wage theft to ever hit the fashion industry.

More than 400,000 garment workers in Karnataka have not been paid the state’s legal minimum wage since April 2020, according to an international labour rights organisation that monitors working conditions in factories.

The Worker Rights Consortium (WRC) estimates the total amount of unpaid wages so far to be more than £41m.

One worker said she only earned about half of what she needed to cover basic living costs, such as food and rent.

“If we had got the wage increase last year, we could have at least eaten vegetables a few times a month. Throughout this year I have only fed my family rice and chutney sauce,” she said.

“I tried to talk to the factory management about it,” she added, “but they said, ‘this is what we pay to work here. If you don’t like it, you can leave.’”

Scott Nova, executive director of the WRC, said: “In terms of number of workers affected and total money stolen, this is the most egregious act of wage theft we’ve ever seen. The children of garment workers are going hungry so brands can make a buck.”

Karnataka is one of India’s garment-industry heartlands, with thousands of factories and hundreds of thousands of workers producing clothing for international brands including Puma, Nike, Zara, Tesco, C&A, Gap, Marks & Spencer and H&M.

Nova said the “indifference and inaction” of all the brands sourcing clothing from the region about the situation facing its mostly poor, female workforce was “shameful and cruel”.

He said that despite persistent demands from the WRC for the past two years, western brands had either refused to intervene or had not acted to ensure that workers making their clothes were paid in line with Indian law.

“It has been almost two years since apparel suppliers have been refusing to pay the legal minimum wage and brands have been letting this continue when they know they are the only ones with the power to stop this widespread wage theft,” he said.

“Payment of minimum wage is pretty much the lowest bar on a brand’s responsibility towards its workforce. If they won’t even insist on this being paid then they are letting a human rights violation on a huge scale continue with impunity.”

The annual cost of living increase to the minimum wage, the “variable dearness allowance” (VDA), was increased to 417 Indian rupees (£4.10) a month in April 2020. The WRC said that as this supplement for low-paid workers, which amounts to 16p a day, had gone unpaid for 20 months, each employee had been underpaid by R8,351 (£83).

Garment suppliers argue that the Ministry of Labour & Employment issued a proclamation suspending the minimum wage increase shortly after it was implemented in April 2020 and that a legal complaint relating to the requirement to pay the increase was still progressing through the courts in Karnataka.

However, in September last year, the Karnataka high court ruled that the labour ministry’s proclamation was illegal and that the minimum wage, including all arrears, must be paid to workers regardless of any other court proceedings.

According to the WRC, apparel suppliers make up the only industrial sector across Karnataka refusing to comply with this court order.

Workers in Karnataka, whom the Guardian are not naming to protect their livelihoods, said that not receiving their pay rise, in the face of steeply rising living costs, had had a devastating effect on their own lives and those of their families, especially their children.

Another woman, who works at a factory making clothing for UK high street brands, said that she had been forced to leave her home and was now living with a relative because she could no longer pay the rent.

“The salary increases we received every year didn’t cover our living costs but did help with things like food for the family and medicine. Working in the garment factories is very painful.

“The brands who buy from my factory demand quality and for the clothes to be shipped in time but aren’t bothered with what happens to me,” she said.

Puma, Nike, Gap, Tesco, C&A, Marks & Spencer and H&M, which are among the brands sourcing clothing from Karnataka, all said that they were committed to paying the legal minimum wage and expected their suppliers to comply with the high court order.

H&M said: “We have made it clear to our suppliers in Karnataka that they must pay the workers legally mandated minimum wages, including all arrears. If they fail to do so, it will ultimately lead to serious business consequences.”

Gap said in a statement: “[We] expect our suppliers to comply with the VDA allowance and arrears. We have established a timeline by which we expect full compliance.”

C&A said in a statement that it had demanded its suppliers comply with the court order and it was “confident” that they would do so. The Dutch-owned multinational said it was expecting written confirmation from its suppliers.

Marks & Spencer said it was working with the Ethical Trading Initiative to “demand” that its suppliers paid the legal minimum wage.

“We have engaged our suppliers in the state directly, making clear our expectation that these conditions be met with immediate effect,” an M&S spokesperson said.

Puma said that its influence on its suppliers was “limited” in Karnataka but added: “We are working with our peers, who source bigger volumes in Karnataka, to make sure that wages are paid correctly.”

Nike said in a statement: “Nike expects all suppliers to comply with local legal requirements and the Nike code of conduct.”

A spokesperson for Tesco said: “We are working with the Ethical Trading Initiative and other brands to ensure this issue is resolved and workers are paid in full.”

A spokesperson for Inditex, which owns Zara, said: “Inditex has a stringent code of conduct, which requires all factories in our supply chain to pay legal wages as a minimum. We are engaging suppliers in the region to urge them to make the VDA payment.”

The statement added: “Wages should always be enough to meet at least the basic needs of workers and their families.”