Growing criminal networks are profiteering from illegal fly-tipping across the UK, an investigation has found.

Unlicensed companies are advertising waste removal services online on Gumtree and then charging consumers to collect their rubbish before dumping it elsewhere in the country, according to findings from Channel 4’s Dispatches programme.

In the UK, it is illegal for waste removal companies to operate unless they are registered with the Environment Agency and have a licence.

However, the investigation found that less than 20% of Gumtree adverts analysed appeared to be posted by firms with a licence.

Around half of the adverts from what seemed to be different, unlicensed companies were also found to be linked – pointing to two organised criminal networks,

Dispatches calculated that one van, picking up waste every day and dumping it, could be making more than £145,000 in extra, illegal profits, each year.

Elsewhere, an exclusive survey by the National Farmers Union, which asked 620 farmers across England and Wales about fly-tipping, found that 50% have experienced a small-scale fly-tipping event.

More than a quarter of all those surveyed have had a large fly-tipping incident on their farm, it found.

Rachel Hallos, vice president of the National Farmers Union, told the programme: “Ultimately, it’s people that are cheating in the system. And they shouldn’t get away with it.”

Satellite surveillance and site visits were also undertaken for Dispatches and uncovered 50 potential waste dumps in the South East worthy of further investigation.

Of the 50 sites, 25 had no waste permits, the investigation found, suggesting there could be thousands across the UK.

Dispatches also went undercover to find out what happens when some of these unlicensed waste removal companies are hired to dispose of items, placing GPS trackers and ultraviolet markings on waste items.

The team confirmed that despite paying for an advertised waste removal service, many of these items were in fact being dumped elsewhere in the country.

When challenged on camera about this discovery, the companies denied fly-tipping or refused to respond.

The investigation uncovered what appeared to be a large, nationwide network of fly-tippers, which has its own app.

Kevan Jones, a former MP who has campaigned alongside politicians from all the major parties for more to be done about waste crime, said: “Sixty of the top organised crime groups in the UK are involved.

“They’ll go where they can make easy money and for them, this is easy money. There’s no deterrent at all because there’s very little enforcement of it.”

Anna Willetts, an environmental criminal defence lawyer who has worked on high-profile waste crime cases for the last 20 years, said: “Waste is built up over a number of years, completely uncontrolled, deposited regularly by waste criminals, no permits, no controls in place.”

She added: “The sharp end of waste crime does go hand in hand with a lot of other criminal activity, including firearms, drug offences, child trafficking and modern slavery.”

The Environment Agency said: “This is not an easy fight – but with the support of our partners we are working to keep one step ahead of the criminals, shut them out of the system and move us towards an economy in which there is no space for waste crime.”

“Waste crime causes harm to people and places, and it is on the rise,” it said.

“This is why we have a robust strategy which is intelligence-led, collaborative and high-tech, including drones for surveillance and heat-sensitive cameras to identify what is in shipping containers or warehouses.”

In Rubbish Tip Britain will air at 8pm on Channel 4.