Safe Car Wash was launched by the C of E's anti-slavery campaign The Clewer Initiative and the Catholic Church's Santa Marta Group last June.
New analysis by the University of Nottingham's Rights Lab also reveals the application was downloaded 8,225 times during its first six months.
Chair of The Clewer Initiative, Bishop Alastair Redfern said: "This research shows that the Safe Car Wash app has made an excellent start towards mapping the extent of modern slavery and labour exploitation in hand car washes, and, crucially raising public awareness of this issue.
"Sadly, the findings so far confirm what we already feared - that many car washes do not protect their workers."
Customers concerned by working conditions at a hand car wash have been urged to download the Safe Car Wash app and complete a survey which includes key indicators of modern slavery.
It asks the user to consider whether staff members are equipped with appropriate protective clothing - such as gloves and boots - and whether there is evidence of staff living on site.
Today a report from the University of Nottingham's Rights Lab into the data from the Safe Car Wash app is published! Read the highlights and download the report: https://t.co/UqGox1ybHf pic.twitter.com/VsxtOj2oTJ— Clewer Initiative (@theclewer) April 7, 2019
Bishop Patrick Lynch, from the Santa Marta Group, said: "I welcome this report into the results of the Safe Car Wash app.
"I hope the app and this report will help many people become much more aware of the exploitation that workers in the car washing sector often have to endure."
Based on answers received, the app will then alert the user to the likelihood modern slavery. If the offence is suspected, the anonymous results are passed on to police and the Gangmasters' and Labour Abuse Authority.
Drivers using #SafeCarWash app to gather information on modern slavery in hand car washes made more than 900 reports of potential cases over a five-month period, according to Nottingham University research published today.— Santa Marta Group (@santamartagroup) April 7, 2019
Read more: https://t.co/ZFpP3QD7h1#ModernSlavery
Dr Akilah Jardine, Research Associate at the Rights Lab, said: "Investigations and operations on hand car wash activities have identified the sector as a high-risk area for labour exploitation.
"Though often operating in plain sight, a great challenge in tackling abuses is the lack of data on the size and scope of the industry and the nature and prevalence of labour exploitation.
"The Safe Car Wash app shows the potential value of using technology in raising public awareness and leveraging the real life experience and insight of the community to improve our understanding of the sector and also gather the intelligence required to lead effective investigations."
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