There is an ominous new arrival in the tropical forest outside Yenagoa in the southern Nigerian state of Bayelsa. It travels on black metal stilts above the green canopy before sinking into a concrete bunker where, when the bulldozers and cranes have finished work, millions of cubic feet of natural gas will be pumped before going up in smoke.

Shell's Opolo-Epie facility is the newest gas flare in the Niger Delta. And it gives the lie to claims from oil multinationals and the Nigerian government that they are close to bringing an end to the destructive and wasteful practice of gas flaring.

"This is environmental racism," said Alagoa Morris, an investigator with a local group, Environmental Rights Action, who regularly risks arrest to monitor activities at the heavily guarded oil and gas installations. "What we are asking for is that oil companies should have to meet the same standards in Nigeria that they do operating in their own countries."

The Opolo-Epie plant is set to join at least 100 other flares burning across the swamps, creeks and forests of this oil-producing region, filling the atmosphere with toxins, seeding the clouds with acid rain and polluting the soil.

The gas flares, some of which have been burning constantly since the 1960s, are visible from space. In a country where more than 60 per cent of the people have no reliable electricity supply, the satellite images show the flares burning more brightly than the lights of Nigeria's biggest city, Lagos.

Medical studies have shown the gas burners contribute to an average life expectancy in the Delta region of 43 years. The area also has Nigeria's highest infant mortality rate – 12 per cent of newborns fail to see out their first year.

The process of burning off unwanted "associated gas" brought up when oil is pumped out of the ground has been illegal in Nigeria since 1984. The government has set three separate deadlines for stopping the practice – the latest of which falls due at the end of this year – but still it continues.

While Nigerian officials are claiming record reductions in the amount of gas flared, independent oil and gas experts believe flaring is, in fact, reaching historic highs. Many observers attribute last year's much-trumpeted reduction to militancy in the Niger Delta which halved oil production.

"There is an obvious correlation between militancy, reduced oil production and reduced flaring," explained Joseph Hurstcroft, executive director of Stakeholder Democracy Network, a respected rights group working in the region. "The figures in the Delta are never clear but we are expecting to see an increase in flaring now that production is back up."

The Nigerian National Petroleum Corporation (NNPC) claims to have reduced flaring to 1.9 billion standard cubic feet (bscf) per day, or 30 per cent of total production. But a confidential report by international energy consultants, seen by The Independent, puts the figure at 2.5 bscf, or 40 per cent of total production.

The scale of the waste is staggering. If put through a modern, combined-cycle power station, this quantity of natural gas could fuel about a quarter of Britain's power needs. It is equivalent to more than one third of the natural gas produced in the UK's North Sea oil and gas fields and would meet the entire energy requirements of German industry.

The pollution generated from this flaring has been measured at up to 50 million tonnes of carbon dioxide, with unknown quantities of the far more damaging greenhouse gas: methane.

What is going on in the Niger Delta is a "continuing economic, political and environmental disaster", according to Chris Cragg, an independent oil and gas expert. "It is one of the largest single pointless emissions of greenhouse gas on the planet, with obvious implications for climate change that will not only affect Nigeria, but also the rest of the world."

Nigeria boasts some of the largest reserves of sweet and easily refined crude oil anywhere on the planet. Despite the scale of its oil stocks, it has far larger amounts of gas and is sometimes described as a gas province with some oil attached. Historically, it was the high-value crude which drew companies to the swampy Niger Delta in the 1950s when no one was interested in natural gas. While other countries have since created markets and infrastructure to utilise the gas, Nigeria has lagged behind, with successive governments content to impose largely meaningless fines on an industry that provides 80 per cent of the nation's income and more than 90 per cent of its export earnings.

Oil companies such as Shell, Exxon, Chevron and Agip argue that the absence of a domestic market, the imposition of price controls and the high cost of building infrastructure to capture and distribute natural gas have made it economically unviable to end flaring. They complain that they are forced to operate as minority partners in joint ventures with the NNPC, which consistently fails to provide its share of investment. The Nigerian government, which has a bill going through the Senate demanding an end to gas flaring at all facilities by 31 December, has in turn blamed the oil majors.

"You will never completely eliminate flaring," said Bent Svensson, of the global gas flaring reduction unit at the World Bank. He said the best that could be hoped for was the elimination of "continuous flaring" – the most damaging way to dispose of associated gas. "That is at least four years away and that assumes everything goes according to plan, and there have been plans and deadlines before," he added.

Shell told The Independent it had spent $3bn since 2001 on a "flares-down" investment programme and insisted that any new plants, including Opolo-Epie, used flares only for safety reasons. However, the company made an identical spending claim in a public report more than three years ago, suggesting it has either spent nothing in the last three years or that it overstated the level of that investment.

"The companies are not serious at all about ending flaring," said Nnimmo Bassey, a Nigerian environmental activist who chairs Friends of the Earth International. "They will never stop gas flaring until the oil wells run dry."

WHAT IS GAS FLARING?

*Geology dictates that some of the richest deposits of oil sit together with deposits of natural gas. Gas flaring is the practice of burning off that natural gas when it is brought to the surface in places where there is no infrastructure to make use of it. In the 1960s and 70s, "worthless" gas was continuously flared at oil wells from Texas to Saudi Arabia. At its peak, the practice pumped about 110 million metric tonnes of carbon dioxide to the atmosphere each year — about 0.5 per cent of the world's carbon dioxide emissions.