£2.6 billion a year is spent on initiatives to improve energy use, but most homes still leave on lights.

A report by the National Audit Office (NAO) shows a typical household could save 30 per cent, or £280 a year, from their energy bills, but that 71 per cent of households leave appliances on standby, 63 per cent forget to turn lights off in rooms and 28 per cent leave heating on when their house is unoccupied.

In total UK households now spend £20 billion on energy each year.

The energy efficiency of households improved by 19 per cent between 1990 and 2004, but the NAO found this improvement was offset by a rise in household energy consumption, as the number of smaller homes grew along with the use of consumer electronics.

However, since 2004 energy use has started to fall.

The government target is to cut total energy consumption by nine per cent by 2010 compared with average 2001-2005 levels and for homes to be 20 per cent more energy efficient in 2010 than they were in 2000.

NAO head Tim Burr said: “There are encouraging signs the long-term growth in household energy consumption is reversing.

“But most of us still forget to turn off the lights in empty rooms, and building regulations to save energy in homes are not always followed.”

He added: “If targets are to be met, departments need to improve their understanding of how programmes are working in real homes, and how householders are responding to them.”

The report found the obligation on energy suppliers to provide energy efficiency measures had been successful, particularly in targeting vulnerable households.

However, there were concerns about the capability of suppliers to meet the required installation rates of loft and cavity wall insulation.

The report concludes, to achieve their longer-term targets, programmes must focus increasingly on homes that are harder to treat, technologies that are newer and more expensive, and householders who are less keen to act.