Drivers are being urged to report signs of modern slavery at cheap hand car washes using a new smartphone app.
Safe Car Wash asks motorists about a series of indicators of forced labour including the use of children, fearful behaviour, a lack of protective clothing and prices lower than £6.70.
It sends the anonymised data and a GPS position to the National Crime Agency (NCA) and the Gangmasters and Labour Abuse Authority (GLAA) and directs users to the Modern Slavery Helpline.
The app, which is available for download from 4 June, has been launched by The Clewer Initiative, the Church of England's campaign against modern slavery, and the Santa Marta Group, the Catholic Church's anti-slavery project.
It is estimated that there are more than 18,000 hand car washes on Britain's high streets, at the sides of motorways, and on abandoned garage forecourts.
While many run as legitimate businesses, some exploit, force and threaten workers, according to campaigners – but there is no reliable data on the scale of the problem.
The Archbishop of Canterbury, Justin Welby, said: "Over the last few years we have learnt more about the evil of modern slavery and we have begun to understand how it is perpetrated in our communities in plain sight.
"Through the Safe Car Wash App we now have a chance to help tackle this scourge which is damaging so many people's lives."
Cardinal Vincent Nichols, the Archbishop of Westminster, welcomed the "very helpful and timely initiative in an area of real exploitation".
"As we learn to see this example of forced labour and modern slavery in our midst, we will also become more aware of the presence of this evil scourge in other sectors in our neighbourhood," he added.
The app is described on its website as "a new tool that will enable the largest community intelligence gathering exercise ever attempted in the United Kingdom."
Will Kerr, director of vulnerabilities at the NCA, said the app will "help law enforcement identify those people who may be at risk, as well as those criminals who are exploiting the vulnerable".
And interim GLAA chief executive Roger Bannister added that the app is a "great way of utilising the technology so many of us have become accustomed to".
The data gathered by the app will be collected and analysed over a six-month period by the University of Nottingham's Rights Lab, who will report back in early 2019.
Professor Zoe Trodd, director of the Rights Lab, said: "Car washes are completely unregulated territory and we don't know how big the sector is, how many hand car washes operate or how many persons are registered to work in them.
"This citizen engagement in data collection is a powerful technique with potential for mapping other vulnerable services such as nail bars."
Last year the Independent ran a special investigation into modern slavery, Slaves on our Streets.
The Press Association contributed to this report
