The 0.1% reduction differs from an estimated 0.25% increase given in provisional figures last March.
The provisional figures indicated a reduction of 5.3% in CO2 since 1990 but this has now been revised to 6.4%. Total emissions are down to 554.2 million tonnes in 2005 from a baseline of 592.1 in 1990.
The figures do not signal a return to the previous marked downward trend. The margin of error of at least 0.5% means the reported 0.1% fall could be insignificant, and the figures include reductions from carbon sinks.
Nonetheless, household CO2 emissions were 4.6% lower in 2005 than in 2004. Environment Secretary David Miliband called the decrease "a hopeful sign", but cautioned that it would take several years to confirm whether it signalled the start of a downward trend.
Meanwhile, emissions increased by 0.9% in the energy sector as the high price of gas encouraged power generators to burn more coal. Other industries also burnt more coal adding 0.6% to emissions. Road transport CO2 emissions rose by 4%, and the sector's nitrous oxide emissions have increased five-fold since 1990.
With allowances under the EU emissions trading scheme taken into account, the UK looks set to achieve a 16.2 % cut in CO2 by 2010 – short of its 20% target.
Emissions of the basket of greenhouse gases covered by the Kyoto Protocol fell by 15.3% between 1990 and 2005. This exceeds the UK target of a 12.5% reduction by 2012.
Emissions of fluorinated compounds fell 38% over a decade, but increased by 0.4 million tonnes of CO2-equivalent in 2005.