By failing to meet the legal requirements for energy efficiency, one in 10 new homes condemn their owners to higher energy bills and contribute towards climate change.

The government has identified improving households’ energy efficiency as the best way to reduce carbon emissions at the same time as keeping a lid on rising utility bills.

Since April 2008, all new homes have had to meet tough standards on draught proofing, lighting and heating. All homes require an Energy Performance Certificate (EPC)indicating how they rate. But at least 30,000 of the 300,000 homes built since then do not meet these legal standards, according to official figures just released.

Andrew Warren, director of the Association for the Conservation of Energy, said: “Buying a home is the biggest single purchase people will make in their lives. With energy costs mounting – never mind the environmental issues – it’s perfectly respectable to expect that buildings meet the minimum legal standards for energy efficiency.”

A spokeswoman for the Department of Communities and Local Government (CLG) said she was not aware of any builders or companies being prosecuted for failure to comply with new standards. Local authorities are in charge of compliance. She said that new homes failing to meet the standards can still be used and sold and suggested that a possible explanation for the large number of homes that fail to meet new standards might be that conversions of existing buildings, such as a barns, do not have to comply fully.

According to the junior housing minister Ian Austin, 743 new homes built since April 2008 are rated in the top EPC band. About 180,000 homes are rated in band B, and 89,000 are rated in band C. New homes built must be at least a band C, with higher requirements for housing association and council homes. The government figures do not divide private and public sector housing.

Experts are sceptical about the accuracy of these official figures. Energy efficiency assessments are carried out by local government inspectors, or increasingly, poorly regulated private sector assessors hired by developers. The government announced recently that in future new homes would have to be 25% more energy efficient than existing rules stipulate.

By Nina Massey