About a third of companies are not doing enough to identify slavery in their operations, such as carrying out site visits and ensuring workers receive the minimum wage, the survey by the Chartered Institute of Procurement and Supply (CIPS) found.
Regarded as a global leader in the drive to end slavery, Britain passed the Modern Slavery Act in 2015 to crack down on traffickers, force businesses to check their supply chains for forced labour and protect people at risk of being enslaved.
Yet companies have been slow to react and introduce anti-slavery policies, with little to no progress made over the last year alone, showed the CIPS survey of 900 supply chain managers.
"Eliminating human suffering is not something that can be done on a piece of paper," CIPS group director Cath Hill said in a statement. "There needs to be a change in mindset."
"Instead of seeing modern slavery prevention as an annual compliance exercise, business and government must integrate it into the way they conduct due diligence every day," she added.
Almost a third of supply chain managers surveyed by trade body CIPS said they faced greater pressure to find modern slavery but had no extra resources to do so, while seven in 10 wanted more guidance and training on how to tackle the problem.
The Modern Slavery Act requires firms with a turnover of at least 36 million pounds to produce an annual statement showing what they have done to ensure their operations are slavery-free.
Just over half of the about 19,000 companies in Britain required to comply with the law have issued statements to date, according to Transparency in the Supply Chain, a public database.
"Far too many (companies) appear to treat it as a box ticking exercise," Patricia Carrier, modern slavery project manager at pressure group The Business and Human Rights Resource Centre, told the Thomson Reuters Foundation by email.
Britain should hold firms to account by producing a public register of those that have produced statements, and ensure its public suppliers respect the law, said Neill Wilkins, programme manager at the Institute for Human Rights and Business.
The interior ministry says it is working to raise awareness of the law through a campaign targeting about 10,000 businesses.
Britain is home to about 136,000 modern slaves - trapped in forced labour, sex exploitation and forced marriages - found the 2018 Global Slavery Index by rights group Walk Free Foundation.
Modern slavery in Britain mainly affects immigrants and vulnerable people, often working at car washes, construction sites, hotels, nail bars and farms, according to the Gangmasters and Labour Abuse Authority - its anti-slavery body.- Thomson Reuters Foundation
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