The level of greenhouse gases is rising rapidly and far greater global efforts are needed to tackle the issue, a leaked UN report has warned.

The report by the Intergovernmental Panel on Climate Change says hugely expensive technology will be needed if the current situation continues.

It says CO2 gases grew by 2.2% per year on average in 2000-2010 - almost twice as high as in 1970-2000.

The UN says the paper - to be published in April - is a work in progress.

The leaked IPCC draft report urges the world community to act without delay to cut emissions and shift to clean energy.

If CO2 gases are allowed to continue growing at their current rate, increased conservation and efficiency would not be sufficient to counter their impact, the document says.

It accuses governments of spending far more on subsiding fossil fuels than switching to cleaner energy.

And the document identifies economic growth and population growth as two main drivers for the rising greenhouse emissions.

In 2009, politicians from around the world took a decision at the Copenhagen climate conference to try to limit long-term global average temperature increases to 2C (36F).

This, it was said, was the point above which dangerous changes to the planet would occur.