Once upon a time, a trip to the local car wash involved buying a token, driving into a fixed machine and sitting patiently while two large, colourful brushes whizzed back and forth until the vehicle was clean.

Nowadays, it is more likely to comprise a bargain basement 'full valet' deal on low-cost premises. The token has been swapped for a cash-only exchange and the brushes replaced by an army of young, non-English speaking men stopping only for the occasional cigarette or fizzy drink.

While our cars will emerge clean, our consciences may not, because these modern day car washes are also rife with modern slavery.

Many workers are trafficked into the UK on the promise of paid employment before becoming trapped in debt bondage, owing money to their car wash bosses which they stand no chance of ever repaying. It is a form of slavery which is in plain sight of so many of us and therefore the responsibility of all of us to address it.

Recently, I've been working with the Petrol Retailers Association (PRA) to develop intelligence on the prevalence of unregulated car washes across the UK. The PRA advises businesses and represents companies that install car washes to ensure they are compliant with health and safety regulations, insurance requirements and environmental legislation.

I have also raised the issue with local authorities, police and the media. As a result, the Mirror newspaper went on to conduct an investigation which found evidence to reinforce the fear that thousands of mainly Eastern European nationals could be trapped working on forecourts and in car parks. Journalists visited 10 hand car washes and found all displayed tell-tale signs of slavery. Unable to speak English, so-called employees can work for up to 11 hours a day for little or no pay, and when their shift is done, they go 'home' to makeshift accommodation, sometimes made from shipping containers. Those who try to quit are threatened with violence or even deportation.

So how do we spot the signs of slavery at our local car wash? They can include:

Lack of protective clothing

Unprofessional facilities

3 or more people washing single cars

Staff unfamiliar with the English language

Signs that people both live and work on site

If your local car wash demonstrates some of these signs, please do not look the other way. Poor construction and hazardous electrical supplies are not simply a breach of health and safety policy, they are potentially slave-like conditions that are a risk to human life. The Times reported on a fatal case of this at the beginning of the year, when a car wash worker died while taking a shower on a car wash site - both his place of work and his home.

Call the police if you think someone needs urgent help; contact the Gangmaster and Labour Abuse Authority or Crimestoppers to confidentially report a crime; or reach out to the Modern Slavery Helpline for advice on how to respond to a potential case of modern slavery.

You may feel delighted that your car has been cleaned for a bargain but somebody else is paying a high price.