Officers found four sites where waste had been burnt illegally, a further four which were actively and illegally treating and transferring waste, and a number containing construction and demolition waste.

Among the rubbish, officers observed shredded plastics, soil, rubble, scrap metal, tyres, pallets – and, at one site, a number of discarded toilets.

Some of the sites contained overflowing skips and more than 5,000 tonnes of waste being stored illegally.

A total of 54 sites were visited by officers with only half of them found to be operating within the law.

Pete Stark, Environment Agency Enforcement team leader, said: “We will be following up on every single site where we’ve found illegal activity so we can put a stop to activities that blight our neighbourhoods, our environment and our economy.

“Working closely with HMRC to investigate these reports from local communities has helped us strengthen our working relationship, identify sites of interest, and prevent and disrupt crime that puts people, wildlife and legitimate businesses at risk.

“We take waste crime extremely seriously, and formal investigations into these sites are now underway.”

If convicted of illegal waste activity, offenders face unlimited fines and up to five years in prison.