Hand car wash sites in northern England have been the focus of a major crackdown on slavery by the National Crime Agency (NCA), targeting organised crime in four countries.

Officers from the NCA, the North East Regional Special Operations Unit, Cleveland, Northumbria, Sussex and Metropolitan police forces arrested 21 people at addresses across the North East, South Coast and London.

The strike was one of the NCA’s biggest since it began operations in 2013, with around 350 officers from the agency and its partners taking part.

It followed an NCA investigation into a Kurdish network suspected of smuggling people to the UK from France, Belgium and the Netherlands.

The NCA worked closely with the French Police Aux Frontières (PAF), the Belgian Federal Police and Dutch Kmar in the year-long investigation which led up to the strike.

Agents linked to the network are alleged to have recruited drivers both on the Continent and in Teesside.

Over the past year the NCA’s officers, in partnership with Immigration Enforcement, Border Force and European partners, have stopped several drivers and safeguarded migrants found on board their vehicles.

About 60 officers from the NCA, Durham, Cleveland and Northumbria police, Immigration Enforcement, HMRC and the Gangmasters and Labour Abuse Authority carried out spot-inspections of hand car washes in the area.

NCA deputy ddirector Tom Dowdall said: “The number of officers deployed today by the National Crime Agency, the police and partner agencies reflects the scale and severity of the suspected criminality.

“It is one of the biggest operations of its kind undertaken by the NCA.

“We believe we have identified and disrupted a significant network which is suspected of smuggling hundreds of migrants into the UK and planned to carry on going.

“People smugglers don’t think twice about putting lives in danger, employing a range of dangerous methods as they attempt to evade border controls.

“It is a crime predicated on exploitation of vulnerable people and their treatment as a commodity instead of as human beings.

“If anyone in the local community thinks they have information about linked criminality in the area we’d urge them to call the local police.”

The investigation was part of Project Invigor, an NCA-led campaign to tackle organised immigration crime.

The Project Invigor taskforce, led by the NCA, includes officers from Immigration Enforcement, Border Force, and the Crown Prosecution Service. It works with international partners to target suspected criminal networks behind people smuggling in the Mediterranean and at the UK border.

Cleveland Police superintendent Sharon Cooney said: “We are pleased to have been able to work alongside the NCA as part of a national operation around people smuggling.

“These crimes are not confined to our local towns and communities; they are national and international and require the highest level of response.

“We will continue to work with our communities and regional and national policing colleagues to ensure that people smuggling, the exploitation of the most vulnerable by the most ruthless, will not be accepted.”

A spokesman for the French Office of the Prosecutor said: “This investigation was carried out in close cooperation with the French judiciary, specifically the Prosecutor in Boulogne-sur-Mer, Pascal Marconville, lead for the fight against organised immigration crime from Calais to the UK.”