The government department that runs energy policy has offices in highly energy inefficient buildings, BBC Freedom of Information requests show.
Four of the eleven offices leased by the Department of Business, Energy and Industrial Strategy (BEIS) received the lowest G rating.
The energy display ratings are used to measure the energy performance of public buildings.
The department said it had made progress in cutting emissions.
The display energy certificates show 10 Victoria Street, in Westminster, which the department leases and operates, uses twice the amount of electricity a typical office of that type would do.
Its offices at Apex Court in Nottingham, Cheylsemore House South in Coventry, and Buckingham Palace Road in central London, also received the lowest possible G rating on their certificates.
Only one building the department leases, The Observatory in Chatham, received an A rating, and the department’s headquarters, at 1 Victoria Street, scored below average, with an E rating.
Julie Godefroy, head of sustainability development at the Chartered Institution of Building Services Engineers, which produces guidance on how to improve building use, said this energy inefficiency was a missed opportunity to provide leadership on making buildings less wasteful.
“Any building on this (G) scale is being operated inefficiently, meaning there are energy and carbon emissions that could be avoided, and costs savings missed for us as taxpayers,” she said.
Sian Berry, Green Party London Assembly member, said: “An energy department that can’t be bothered to improve the awful energy rating for their London offices shows a complete indifference to what’s happening in their own back yard.
“We shouldn’t really be surprised to see the ‘green’ department being so careless when the same government is also making climate-wrecking decisions on green energy projects, road building, fracking and Heathrow.”
Last October, Business and Energy Secretary Greg Clark put plans to increase energy efficiency in homes and businesses at the heart of his Clean Growth Strategy to curb carbon dioxide emissions.
A spokesperson for his department said: “BEIS exceeded its target to reduce emissions by 40% by 2019/20 three years early. We achieved 51% reduction in emissions in 2016/17, and made £104m in savings across government in the last financial year through efficiency measures and streamlining of the estate.”
They also said that at 10 Victoria Street the department was installing double glazing and replacing the boiler system with a modern energy efficient one.