LONDON: Benchmark European Union carbon prices fell to a record low earlier this month, as prospects of a slowing economy eroded demand in market analysts say is oversupplied with hundreds of millions of carbon permits and credits.

The EU Emissions Trading Scheme caps the emissions of some 11,000 factories and power plants in the bloc, forcing them to buy carbon permits to cover their emissions output.

But since the start of the year carbon prices have shed half their value to below 7 euros per tonne, prompting some calls for EU officials to rescue the beleaguered market.

On Dec. 20, EU lawmakers backed a proposal to let the bloc\'s executive Commission prop up record low carbon prices by withholding 1.4 billion permits from the third phase of its Emissions Trading Scheme, sending the prices 20 percent higher. The intraday move was more than 30 percent.

It may take months of political wrangling to determine whether any intervention measures should be taken to help balance supply and demand in the third phase (2013-2020), meaning carbon prices are expected to remain volatile in the meantime.

Below is a list of the benchmark carbon contract\'s top five most volatile trading days since 2008, as measured in percentage terms of its intraday peaks and troughs, according to Reuters data. This is accompanied by a brief reason for the price spike.