LONDON (Reuters) - The way companies report their greenhouse gas emissions is extremely inconsistent, a study by research body the Environmental Investment Organisation (EIO) showed on Wednesday.
The EIO ranked the UK's 100 largest companies according to their emissions intensity and how transparent they are in reporting emissions output. The rankings are designed to lower corporate emissions by influencing a company's share price.
Insurer Amlin topped the rankings with the lowest emissions intensity of 1.21 metric tonnes of carbon dioxide equivalent for every million dollars of turnover.
West African-focussed gold producer Randgold Resources was at the bottom with 3,477.34 metric tonnes -- more than double the top 30 firms combined.
Other firms with the lowest emissions intensities include financial services company Aviva, investment manager Man Group, TV group BSkyB and energy consultancy AMEC.
Insurers Legal and General and Prudential had very low emissions intensities of 0.27 and 0.82 metric tonnes respectively, but failed to verify their data with an independent third party.
"Had their data been verified ... they would be in first and second place. The rankings highlight that carbon reporting is, with few exceptions, extremely inconsistent," the report said.
The report used the most recently available data for each company, EIO said. However, because sustainability reporting does not follow specific patterns, some companies had data for 2010, while some only had data from 2008 and 2009.
The report also found only 35 percent of companies publicly disclose complete and independently verified emissions data, while 13 percent do not disclose their figures publicly at all.
Among sectors, materials had the highest average emissions intensity at 967 metric tonnes per million dollars of turnover -- more than double the energy sector which had 399 metric tonnes. But both sectors had high levels of disclosure.
Among energy companies and utilities, oil giant Royal Dutch Shell ranked 29th, Centrica Plc was 62nd and BP was 84th.
"The rankings show that it's less about what industry a company is in and more about individual attitudes towards transparency. How can Shell and BP be at opposite ends of the table, or Lloyds and Standard Bank?" said Sam Gill, EIO's operational director.
Retailers also had high emissions intensities. Next ranked 16th, Marks and Spencer was 18th and supermarket Tesco was 21st.
The rankings changed somewhat when based on absolute emissions. However, only 66 companies provided complete data on their absolute emissions, the report said.
Although Amlin remained at the top with the lowest absolute emissions, the next lowest emitters included car insurer Admiral Group, investor 3i Group, Man Group and industrial landlord Segro.
The highest absolute emitter was Royal Dutch Shell, which had ranked 29th in terms of emissions intensity.
(Reporting by Nina Chestney; Editing by William Hardy)