US speciality fashion giant Gap Inc has told just-style it is collaborating with unions, governments and industry associations to improve working conditions in the factories that make its clothes after a study found violations at suppliers in India, Indonesia and Cambodia.

The comments came after the retailer was accused of a significant divide between its pledges and actions on factory monitoring and increased regulations to stem abuses across its supply chain.

The allegations were made by the Asia Floor Wage Alliance (AFWA), alongside a coalition of other labour and human rights organisations, a week after the groups criticised Swedish fashion retailer H&M for workplace violations in its supply chains in India and Cambodia.

A spokesperson for Gap Inc said the company has been working for more than two decades to improve working conditions in the factories that make its clothes.

"We know there is more work to be done, but we remain committed to helping ensure that the women and men who make our clothing are treated with dignity and respect," the spokesperson said.

"We know that we can't tackle many of the challenges we face on our own, which is why we are engaging with a wide range of stakeholders – including garment workers, suppliers and factories, employees, unions, governments, multilateral institutions, non-governmental organisations, industry associations, investors, communities and others – to develop solutions that matter most to workers and contribute most directly to improving their lives."

The AFWA research, released ahead of next month's International Labour Organization (ILO) conference in Geneva, was based on interviews with 150 workers in Cambodia, Indonesia and India.

It found that all four Indian factories investigated employed a non-standard workforce, including short-term contract workers, daily wage workers and workers who work on piece-rate. An estimated 60-80% of the garment workforce is employed as contract workers, who lack job security, social security benefits and freedom of association.

The study also said many workers interviewed did not receive regular overtime payments consistent with national standards. Therefore, while minimum wages were met, workers routinely reported underpayment of total earned wages. Wages for workers producing Gap garments in these production hubs consistently fell far short of living wages.

In all four Gap supplier factories investigated, workers said they are forced to do overtime, and that they cannot refuse it. Reported penalties for refusing overtime include dismissal from work and physical and verbal abuse.

Workers who mobilised to demand a living wage met with violent suppression, the report noted, including deadly use of force.

And one in five garment workers – the vast majority of whom are women – experienced sexual harassment including sexual comments and advances, inappropriate touching and bodily contact initiated by both managers and male co-workers.

Gap is also criticised for refusing to disclose factory locations, which means any monitoring reports are impossible to verify. Further, these reports fail to include subcontracted facilities or factories that do not produce goods year-round, which are where the majority of abuses occur.

"There is a clear and substantial divide between Gap's public commitments and the actual implementation of protections in supplier factories," said Anannya Bhattacharjee of the Asia Floor Wage Alliance.

"Workers in these facilities need...Gap and other manufacturers to honour their promises and to provide transparency and movement around efforts to end rights violations throughout the supply chain.

"However, the problem is larger than the Gap. Rights violations are fundamentally linked to the structure of the global garment value chain. The ILO must also take action, set global standards across industries and pass a binding Convention to regulate global supply chains."

The report is one in a series entitled "Workers' Voice from Global Supply Chains: A Report to the ILO 2016," which will detail supply chain malpractices and recommendations for the ILO to amend them through binding regulation.

The group, which includes the international Asia Floor Wage Alliance, Jobs with Justice (USA), National Guestworker Alliance (USA) and the Society for Labour and Development (India) and the Clean Clothes Campaign (EU), will be at the ILO in Geneva to present their findings.

H&M criticised for labour abuses in India and Cambodia