In a report called ‘Coming Clean: Revealing the UK’s True Carbon Footprint’, the charitable organisation says only a fraction of emissions are acknowledged and believes the FTSE 100 index (the top 100 British multi-nationals) may be responsible for up to 12% or even 15% of global emissions, a massive percentage compared to the 2% often quoted by Prime Minister Tony Blair.

“Our research reveals a truly staggering quantity of unreported carbon dioxide is emitted around the world by the top 100 companies on the London Stock Exchange,” said Christian Aid’s senior climate change analyst Andrew Pendleton. “And we don’t even know the extent of the emissions of many of the biggest companies.”

Apparently only 16 of the top 100 PLCs declare their basic emissions leaving much room for discrepancies and inaccuracies.

Pendleton added: “The calculations we have made relate to basics, like offices and lighting, but take no account of investment or supply chains which is a much bigger area. The figures that companies currently declare are such a mess that it is impossible to calculate their total emissions.

“That is why we need clear, reporting standards applied across the board. These guidelines exist already and the government must now make them mandatory.”

Christian Aid wants its supporters to write to Barclays Bank, Morrisons, International Power and Chancellor Gordon Brown calling for companies to declare all emissions to an agreed standard. They also demand companies commit to reducing C02s by 5% per year.