CLAIMS that even small greenhouse gas targets will hurt big industry have been undermined by a government report that found basic efficiency improvements could cut national emissions and save businesses more than $700 million.

An assessment of 199 large energy users found improving efficiency could stop at least 6.4 million tonnes of carbon dioxide from being emitted - a 1.1 per cent cut in the national carbon footprint each year.

The energy savings could run 1.4 million homes for a year and give the companies an extra $736 million.

An industry group, the Energy Efficiency Council, said if the biggest companies improved efficiency by 15 per cent, national emissions would fall by nearly 5 per cent, saving billions in energy costs.

''Economic purists have been telling us that if there were $100 notes lying around, industry would have already picked them up,'' the council chief executive, Rob Murray-Leach, said. ''This report shows that companies have blind spots - sometimes you have to help them find the $100 notes.''