ALMOST half of British homes are not properly insulated, with householders wasting at least £100 a year on their bills as a result, the Government has warned.
Amid rising fuel costs for households, the latest estimates from the Department of Energy and Climate Change (Decc) showed that only 57% of Britain's lofts have been properly insulated.
Only 58% of cavity walls have been filled with insulation, the data showed.
Insulating lofts and walls makes homes more energy efficient, helping people use less energy and save money on their bills, officials said.
The Government is demanding energy companies help some 3.5 million households insulate their homes by December 2012 under obligations imposed on power firms known as the Carbon Emissions Reduction Target (Cert).
Figures show that 479,000 homes have had insulation professionally installed so far under the target.
Energy and Climate Change Secretary Chris Huhne said: "At a time when money is tight and with energy prices predicted to rise, householders are missing out on over £100 of savings every year by not getting their lofts lagged and cavity walls filled.
"We are making energy companies do more to help their customers with another 3.5 million households set to be protected against higher bills by the end of next year."
