The majority of fuel-poor households at the end of 2006 were also classified as "vulnerable", according to ministers.
One million more Britons fell into fuel poverty in 2006, the government has admitted.
The Department for the Environment and the Department for Business released the figures today, showing that 3.5 million people were suffering under their energy costs in this way by the end of the year. Of that total, 2.75 million homes were classified as being "vulnerable" - meaning that they contained someone from an at-risk group such as a child or an old person.
Fuel poverty is commonly defined as when a household spends ten percent or more of its income on energy bills. Correspondingly, consumer gas and electricity costs were found by the government to have risen by 22 percent over that period.
This trend has continued over the intervening period, with most energy firms imposing double-digit increases on their general plans earlier this year. Market leader British Gas even hiked its gas tariff by 35 percent.
Commenting on the figures to the BBC, Tony Woodley at the Unite union said: "The government cannot stand back while struggling households chose whether to heat or eat.
"If intervention is on hand to bail out the speculators and spivs who have caused this economic turmoil, then our government should not have to think twice about helping the frail and vulnerable heat their homes."
