The green technology industry was warned on Thursday that its growth is threatened by a failure to recycle metals and especially rare earth elements.

A U.N.-backed report warned that less than one third of metals globally have a recycling rate of more than 50 percent.

"Many metal recycling rates are discouragingly low, and a recycling society appears no more than a distant hope," said the recycling report by the United Nations Environment Programme (UNEP). "This is especially true for many specialty metals, which are crucial ingredients for key emerging technologies."

The head of the European Union's environment watchdog highlighted the concerns for the emerging green economy.

"All the clean technologies -- batteries, hybrid cars, magnets in wind turbines for example -- they are relying on metals for which we have extremely low rates of recycling," said Jacqueline McGlade, director of the European Environment Agency.

"We have to up our recycling rates," she told the EU Green Week conference.

Shortages of rare earth minerals used in high-tech and defense production, have sent jitters around the world since dominant producer China restricted exports.

The EU is developing a strategy that might include a stockpiling programme for the most critical raw materials.

The UNEP report, which covered all metals, showed one of the highest global recycling rates for lead, mainly from batteries, at around 80 percent, while estimates of iron and steel recycling range from 70 to 90 percent.

Estimates of gold and silver recycling ranged from over 90 percent in the jewelry sector to less than 15 percent in electronics.

"There is virtually no recycling of the rest, including metals like Indium used in semiconductors, energy efficient light emitting diodes (LEDs), advanced medical imaging and photovoltaics," said a UNEP statement.

"The story is similar with other specialty metals like tellurium and selenium, used for high efficiency solar cells, and for neodymium and dysprosium used for wind turbine magnets, lanthanum for hybrid vehicle batteries, and gallium used for LEDs," it added.

McGlade of the EEA pointed to wider issues of heavy consumption in developed countries, and called for smarter use of resources in general.

"What does Europe consume? It's fairly large numbers -- about 16 or 17 tonnes per person per year," she said. "It's four times what someone in Africa uses, three times what somebody in Asia, but it's only half of what people in Australia, Canada and the U.S. use."

That is broken down into around 52 percent minerals, such as construction materials, 23 percent fossil fuels, 21 percent biomass, such as food, and 4 percent metals.