The number of households in fuel poverty rose to 3.5 million in 2006, the latest figures from the Government show.
The figure, an increase of one million on 2005 levels, includes around 2.75 million homes classed as "vulnerable" - containing a child, elderly person or someone with a long-term illness.
The figures, released by the Department for Environment and the Department for Business, mean that 3.5 million households are having to spend more than 10% of their income on heating.
In England, the number of homes in fuel poverty rose from 1.5 million in 2005 to 2.4 million in 2006, including an extra 700,000 vulnerable households.
The Government attributed the rise in the number of households in fuel poverty across the UK to an increase in consumer energy bills of 22% between 2005 and 2006.
Gas prices rose by half from low levels in 2003 to 2006 and electricity prices increased by a third in that time, ministers said.
While the major suppliers cut tariffs early last year, they put them up early this year, and again in the summer.
Environment Minister Hilary Benn said the Government was committed to tackling fuel poverty but that "sharply rising energy price rises have made that goal increasingly difficult". He said that since 2000, the Government has spent £20 billion on fuel poverty benefits and programmes.
Paul Kenny, general secretary of the GMB union, said: "It is imperative that the Government acts on our motion to the Labour conference last week to give the energy regulator the power to cap gas and electricity prices.
"There is no justification for the high prices currently being charged. Somebody has got to get a grip."