There has been a shift towards coal-fired electricity production
Greenhouse gas emissions in Scotland rose by 5.4% in one year, according to new figures.
The increase between 2005 and 2006 was mainly because of a shift to more coal-fired electricity production, due to unstable gas prices.
But the figures showed that overall greenhouse gas emissions had fallen by 13.4% in more than a decade.
They also showed Scottish greenhouse gas accounted for 9.1% of UK net emissions in 2006.
Ministers are aiming to achieve an 80% cut by 2050.
Net greenhouse gas emissions in Scotland increased by 3 million tonnes between 2005 and 2006.
Stewart Stevenson, the climate change minister, said: "This latest data illustrates the scale of action that is required.
"Scotland is a small country, and our emissions can vary due to a variety of factors outwith the government's control such as changes in fuel prices or severe weather."
The figures are contained in the Greenhouse Gas Inventories for England, Scotland, Wales and Northern Ireland: 1990-2006.
In Scotland, the highest emitting sectors were energy supply and transport.
The baseline for 1990 was for carbon dioxide, methane and nitrous oxide and in 1995 for the "F-gases" (hydrofluorocarbons, perfluorocarbons and sulphur hexafluoride).
Energy supply emissions have increased by 7.2% from the 1990/95 baseline, while transport emissions rose by 13.5% from the 1990/95 baseline.
Business remained high, although emissions had fallen by 36.1% from the 1990/95 baseline.
Duncan McLaren, chief executive of Friends of the Earth Scotland, said: "We were expecting this rise in emissions.
"It confirms how urgently the UK and Scottish governments need to address the issue of new coal power.
"If any of the planned new coal power stations are to be built they must have fully operating carbon capture technology from day one."
He said this technology was already up and running successfully in Germany.
"The fact that emissions from transport also increased shows what a big challenge the SNP are facing up to," he added.
"We're interested in how they are going to square their ambitions to cut climate emissions with their enormous investments in transport infrastructure projects.
"Unless the issues around power generation and transport are addressed there is no way Scotland will be able to meet future emissions targets."
Mr Stevenson said the government's commitment to cut Scottish emissions by 80% by 2050 would be framed in law later this year.
"To be successful we all need to make efforts to cut energy, reduce waste and use more sustainable forms of travel," he added.
"One of our first acts on coming to power was to make the renewable energy targets even more stringent - pledging to ensure 31% of our electricity comes from renewable sources by 2011.
"If we add all the potential energy from consented renewable projects to those already operating we will comfortably exceed this target."