Calls for a moratorium on extracting gas from shale rock

There have been calls in the UK for a moratorium on extracting gas from shale rock.

This is a new form of exploiting gas reserves, which is expected to open up large reserves of energy in China, South America and Europe.

But in the US the drilling has been blamed for polluting water supplies and environmental groups want the British government to wait until the technology has been proven safe.

The BBC's Roger Harrabin reports.