The report, issued on Tuesday, is the first estimate of overall emissions for 2006. The government has yet to issue its own figures for 2005.

The government has only published 2006 results for industrial plants, which exceeded their allocation of free carbon emission rights but produced around 4 percent less greenhouse gas than the previous year, the Environment Ministry says.

The CCOO/Worldwatch report is the first estimate of what the country as a whole produced, including households, transport and services -- the sectors with the fastest growing emissions.

Spain's greenhouse gas output in 2005 was 52 percent more than in 1990.

"Since 1990 this is the first time Spain has reduced its greenhouse gase emissions, and it comes in a year of strong economic growth," the report said.

The economy grew 3.9 percent last year, while primary energy use fell 1.3 percent, meaning Spain became more efficient in terms of energy.

Spanish union CCOO's Environment Secretary Joaquin Nieto said the fall in emissions was less a result of government policy and more a result of milder weather, high fossil fuel prices and growth of wind power generation capacity.

"The question is whether this is temporary, or whether we are really seeing a change of direction, in which case we could meet the Kyoto protocol (target)," the report quoted him as saying.

Industry, including power generation, accounts for 45 percent of Spain's CO2 emissions.

CARBON CREDITS

Spain was allowed a 15 percent increase in emissions under the Kyoto protocol because in the 1990s its economy was growing faster than other EU members as it closed the gap in living standards with its richer neighbours.

Its plan for the next phase of Kyoto relies heavily on investing in carbon credits and clean energy projects in developing countries to offset an expected 37 percent increase in its own emissions between 1990 and 2008-12.