Household refuse that is being sent overseas for recycling is being dumped, burnt or strewn across the streets in less developed countries.

Britain exports about 12m tons of material for recycling as part of its environmental waste strategy, but a Sunday Times investigation has found some of these exports – known as “green list” – are being incinerated or dumped in pits.

At one plastics market on the outskirts of Delhi, where all British waste is officially prohibited to help protect the environment, a trader last week showed a reporter a batch of recyclables he had been unable to sell. It included an empty packet of Sainsbury’s Taste the Difference dry-cured unsmoked bacon rashers – a range launched after chef Jamie Oliver started advising the company; a Bernard Matthews turkey ham packet; and a Sungrove orange juice carton. The plastics and other materials that cannot be sold are quietly incinerated.

The recycling industry insists the vast bulk of material sent abroad is used and the environmental impact is monitored closely. However, while regulators say there is a legitimate global trade, they are concerned many of the “green list” exports are not properly sorted or contain materials of mixed quality.

Although English and Welsh councils count all of the materials sent overseas in their official recycling figures, the reality is that a significant proportion is quietly burnt, buried in landfill or simply left strewn on the street. One senior Chinese academic has accused Britain of using his country as a rubbish tip “exporting pollution and turning a profit at the same time”.

Householders are being urged to recycle, but there is almost no demand in this country for some of the waste collected, such as sandwich cartons, yoghurt tubs and plastic trays, and they are traded on the world markets.

Professor Chris Coggins, who runs a waste consultancy, said: “In this country, it would most likely go to landfill so it will get sent overseas. But whether it’s technically legal and whether there’s a market is another question.”

Mundka, a sprawling village on the western edge of Delhi, is one of the destinations for British mixed plastics. It is Asia’s biggest plastic scrap market, although officially no foreign waste is permitted.

Rahul Kumar, a dealer of plastic scrap, last week showed a reporter some of the “left-over” plastics in his yard. Displaying an assortment of containers from Britain, he said: “This stuff will not get much money and we find it difficult to sell.” Plastic bottles are in greater demand, fetching about 15p per pound.

Plastics are recycled by melting and shredding the material, which can then be manufactured into new packaging or products. But some of it is not fit for processing because it is too dirty and damaged or is a “composite” plastic that cannot be reprocessed.

Mohammad Tariq, senior programme officer with Toxics Link, an environment group, said: “Whatever can’t be sold is quietly burnt.” He said there had been a huge fire in an open field in Mundka earlier in the year where traders burnt unwanted plastic, releasing dioxins and other toxins into the air.

“The problem is that this entire process of sorting and recycling is not monitored,” said Tariq. “We want it to be done under the guidance of the rules and norms of the pollution control board, but that is not happening.”

As Britons get into the habit of recycling, waste consultants say the amount of recyclable material being sent overseas is likely to double over the next few years. Some reprocessing companies that handle waste for councils carefully trace and audit the destination of the material they send, but others sell it to agents and brokers and lose track of it.

Some of the containers shipped overseas do not even contain sorted recyclable materials, but an illegal mix of household rubbish, glass and plastics. The Environment Agency has prosecuted companies for this, but the problem of contamination is still understood to be widespread.

Hong Kong is a common destination for Britain’s recyclables. From there, it is often shipped up the Pearl river into China’s Guangdong province where it is sorted. One of the settlements that thrives on this industry is Mai, on the delta of the Pearl river. Once a small village, it is now an industrial sprawl where paper is sorted in small concrete factories and plastic is chopped into pellets for recycling.

Dozens of factories importing mixed British household rubbish relocated to Mai this year after Chinese officials ordered businesses to move from the town of Nanhai, two hours’ drive away in Guangdong, because of an outcry over environmental pollution.

Migrant workers in Mai earn about £1.75 a day sorting the rubbish. Tesco and Sainsbury’s bags flutter in the streets and the waterways are clogged with a rejected and slimy morass of plastic and paper. The streets are strewn with shredded paper and other rubbish.

The materials arriving from Britain are rarely cleanly sorted, as they should be by UK law. “It’s dirty and it’s all mixed together when it arrives,” said Zhang Wulong, 19, a worker in Mai. “The stuff which can’t be recycled is sent to landfill.”

Ma Taiwei, 22, from Guangxi province, who works in another factory, said many of the workers toiled in the belief they would find British money among the rubbish. “I heard of one case where a woman worker found a big bundle of English pound notes,” she said. “I won’t stay here for too long – just until I find some money and then I will go back to my home village.”

Residents complain the recycling industry has had a devastating impact on Mai’s environment. “Everything is polluted,” said Liang Zhi Hua. “Until a few years ago we had clean streams and fields. Now the water is filthy and full of rubbish and chemicals. We can’t grow any vegetables in the fields because they are covered in plastic and waste.”

Although British processors argue China has a huge demand for raw recycling materials, there is growing anger over the environmental cost. Gaoming Jiang, a professor at the Chinese Academy of Sciences’ Institute of Botany, launched a scathing attack on the waste industry earlier this year, saying: “Overseas waste dumping is a classic case of countries exporting their problems.”

The Chinese authorities and British recycling companies are working to ensure materials are processed in designated areas where environmental conditions are carefully monitored. But despite this, the ad hoc and unregulated recycling industry continues to thrive.

Indonesia is another destination for recycling material. The country has had repeated problems with waste being sent from Britain without being properly sorted and now conducts rigorous checks at the port of entry.

Wrap, the organisation that promotes recycling in Britain said the country was, in the main, exporting good quality material. “The idea that Chinese manufacturers are paying the high prices they are for plastics and paper because they want to burn them or bury them and damage their environment is illogical,” it said.

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