About 770,000 households, a third of the total, were placed in that category in 2009, an increase from 618,000 over the previous year.
The term is used when more than 10 per cent of income is spent on household fuel.
The Scottish Government, which published the figures, is committed to wiping out the problem "as far as is reasonably practicable" in the next six years.
The trend has increased each year since 2003-4, when 350,000 households were assessed as fuel-poor.
Housing charity Shelter Scotland said the number brings "shame" on the nation, and warned the 2016 target is likely to be missed.
Housing and communities minister Alex Neil said: "Scotland is leading the way in helping households reduce the amount of fuel they need to buy.
"And another 140,000 hard-pressed households in Scotland have benefited from better insulated and energy-fit homes, saving millions of pounds on fuel bills.
"However, it is bitterly cold and we know many hard-pressed households are struggling with fuel bills."
Graeme Brown, director of Shelter Scotland, said: "For one of the world's more wealthy countries like Scotland to now have more than one third of its households, 770,000, living in fuel poverty or extreme fuel poverty brings shame on our nation.
"If this trend continues the Scottish Government is never going to hit its target of eradicating fuel poverty and certainly has no hope of meeting the 2016 pledge."