Bonded labour in India has been illegal since 1976 but even official figures accept there are still 250,000 people in bonded labour there, many of them working in quarries. Unofficial figures estimate as many as 65million of the sub-continent's billion people work in bonded labour.

Bonded labour is effectively slavery. People, often children, work to pay off family debt. Interest rates are so high the debt is never repaid and people can spend a lifetime in bonded labour. Indeed, families can spend more than a lifetime in bonded labour because the debt is passed down from generation to generation. (You can read how some of the stone industry is tackling the problem here.)

From October, larger stone companies that import stone will have to produce an annual report on what they are doing to identify and eradicate slavery in their supply chain.

The Modern Slavery Act, introduced by Home Secretary Theresa May, received Royal Assent in March and comes into force in October. It includes the 'transparency in supply chains' clause that requires companies to report on their efforts to eliminate 'modern slavery' from their supply chains. 

You can get help about what this could mean from the Ethical Trading Intiiative (ETI), which had called for the clause to be included in the Act.

This week (on 29 July) Prime Minister David Cameron announced what that clause would mean. He said all UK companies with an annual turnover of £36million or more producing goods and services and conducting their businesses in the UK and abroad (which will include stone companies large enough to qualify that import their stone or quartz directly) will be required to complete an annual slavery and trafficking statement.

Within a year from October, all qualifying companies will be expected to share their policies and strategies for tackling slavery publicly.

Cindy Berman, ETI Head of Knowledge & Learning, said: “This is welcome news. The £36million threshold is what we called for in our submission. We believe that by setting it at this level the Government is going a long way to help level the playing field for businesses that are committed to operating ethically. It will avoid the problem of unfair competition from unscrupulous companies that have been operating below the radar and undermining the efforts of socially responsible businesses.

"That’s why ETI’s member companies, together with the trade unions and NGOs, called for this measure and wanted to keep the threshold as low as possible. Our members want to lead by example. We are supporting them to do more than simply manage and mitigate the risks of modern slavery, but to actively prevent slavery from occurring in their supply chains in the first place.”

Cindy said: “This won’t be easy. It will involve a deep dive into the supply chain to understand what’s really going on many tiers down – getting visibility of the many layers to truly see the conditions of workers at the bottom of the chain.

"And where slavery is found, we want companies to be open about it and be recognised for their efforts to investigate, uncover problems and provide remedy.

"The message to companies is clear: it is no longer an option to stay below the radar, refuse to take responsibility for problems in your supply chain and hope you won’t get exposed.

"ETI believes this legislation is a game-changer and can really make the difference in raising the bar on workers’ rights, ending the cycle of exploitation and abuse of workers in the long-term. Workers must be at the heart of these efforts, negotiating their own terms and conditions directly with their employers, with access to redress and grievance mechanisms where their rights have been violated.

"UK businesses have a real opportunity to provide global leadership in driving transparency across their operations and in modelling good practice on preventing modern slavery. We strongly believe this will have a knock-on effect on companies operating in other countries around the world. Collaboration and partnership is key. Modern slavery is an international problem and tackling it requires a concerted and co-ordinated effort on all fronts.

"We also welcome the Government’s forthcoming statutory guidance that will set out expectations for reporting by companies. ETI has offered to help the Government in drafting this guidance, drawing on our extensive experience of tackling abuse and exploitation of workers in global supply chains."