Nike says its factories are obliged to follow company "Code Leadership Standards, which are some of the highest in our industry".
However, the brand was unwilling to outline exactly the level of pay and campaigners say around 80 per cent of garment workers in Indonesia are women earning less than £200 per month.
According to the group, the salaries "do not even cover basic needs". Figures from the Asia Floor Wage estimate a living wage for Indonesia at around £350 per month. It is not known exactly how much workers in the supply chain are paid to produce football shirts for Nike.
Nike guarantees all workers at least the local minimum wage and says it "fully supports union activities across the country", but Clean Clothes, which has been investigating major sporting manufacturers for more than a decade, claims in most cases "less than one per cent" of the price of a jersey goes toward salaries.
"Even in normal circumstances that was never enough to have a modest yet decent living and send their kids to school," Amsterdam-based campaigner Paul Roeland said.
As part of Liverpool's new deal, executives will initially be paid £30m a year - significantly less up front than the likes of Manchester United, who have a £75m deal with adidas. However, the agreement guaranteeing the title winners unprecedented profits on sales has left marketing firms confident that Nike's giant distribution power will lead to record profits.
Concerns over workers rights and the big sporting brands are not limited to football kits. In 2018, the Foul Play report by Clean Clothes compared current production costs of Nike and adidas sport shoes with those of 25 years ago. The share of these costs that ends up in a worker's pocket is now 30 per cent less than in the early Nineties, it was claimed, although it is not known what other costs factor in this figure.
Roeland added: "For over 10 years now, the sports brands have refused to make sure the women and men who make their products are paid fairly; instead they have been left in poverty and many are now laid off."
In response, a Nike spokesperson said: "Wage levels are set by suppliers and vary based on a variety of factors. According to the Nike Code of Conduct, every contract factory employee in the Nike supply chain has the right to compensation sufficient to meet their basic needs and provide some discretionary income. Our suppliers commit to developing and implementing a process that progressively realises this standard over time, which includes providing compensation to factory employees of at least the minimum wage required by country law, or prevailing wage, whichever is higher."
Campaigners from Collectif Ethique sur L'etiquette and Clean Clothes, which also helped expose low pay for up to 10,000 garment workers in Leicester recently, claim talks stalled on pay with Nike and adidas after the brands signed the Indonesian Freedom of Association Protocol in 2011 covering workers' trade union rights.
Raja Siregar, a union member based in Jakarta, said Covid-19 was exacerbating the risk of factory worker poverty.
Nike denied claims that talks had broken down with unions in Indonesia, however, adding in a statement: "Nike has continued to engage with the other stakeholders in the Freedom of Association Protocol in Indonesia since our involvement as one of the original signatories in 2011. Nike continues to fully support union activities across the country and we believe in the importance of strong collaboration between factory management, employees and their elected representatives. Nike also prohibits suppliers in Indonesia from hiring workers on short fixed-term contracts leading to precarious employment."
Most kit suppliers' production factories are in south-east Asia.At adidas, who have agreed a five-year deal with Leeds, they say its "employees in the supply chain are among the highest paid in the industry" and that it is "fully committed to protecting worker rights and to ensuring fair and safe working conditions in factories".
Liverpool said it was inappropriate to comment on Nike working practices as the club are still under contract with New Balance, which failed in legal action against the club last October after claiming executives had refused to honour the terms of a reported £40m-a-year deal.
- Telegraph Media Group