Just 626 homes have completed the installation of energy efficiency measures under the Government's flagship Green Deal programme since it started a year ago, official figures have revealed.
Some 1,612 households had Green Deal plans in progress up to the end of December, with 626 of those having completed the installation of measures such as new, more efficient boilers, solar electricity panels or insulation.
Almost 130,000 homes had been assessed since last January with a view to signing up to the scheme, in which providers meet the upfront costs of installing effiency measures and householders pay the money back from savings they make on their energy bills.
The figures, coming almost a year after the Green Deal launch at the end of January 2013, have prompted warnings that the scheme is not delivering in its current form.
The number of assessments carried out each month peaked in October and fell month on month in November and December.
The figures also show that, up to November, almost 400,000 homes had benefited from measures such as new boilers and cavity and loft insulation under the "ECO" scheme which requires energy companies to provide energy efficiency measures to low-income and vulnerable customers and those in "hard to treat" homes.
Paul King, chief executive of the UK Green Building Council (UKGBC), said: "This latest set of figures, coming a year since the policy launched, should come as a wake-up call to Government that the Green Deal is not delivering in its current form.
"Government must recognise energy efficiency as a national infrastructure priority and be prepared to delve into its purse to make its flagship policy more appealing through stronger incentives and more attractive finance options."
Energy and Climate Change Minister Greg Barker said: "129,842 Green Deal assessments have now taken place with 81% of people consistently telling us that they are taking action following their assessment.
"Thanks to the Green Deal and ECO, over 400,000 households have already been helped to keep warm this winter, demonstrating the potential to transform Britain's housing stock."
Shadow energy and climate change minister Jonathan Reynolds said: "David Cameron's failure to stand up to the energy companies means that people are still desperate for help to get their gas and electricity bills under control.
"We know that improved energy efficiency is one of the best ways to do this but, as these statistics demonstrate, the Government's flagship energy efficiency programme has completely failed, with 99% of people who had a Green Deal assessment refusing to take out a plan.
"Greg Barker, the Climate Change Minister, said himself that he expected 10,000 deals completed by the end of the first year, so he must be asking himself why it has gone so badly wrong."
Trade union Unison called for a house-by-house, street-by-street drive to deliver energy savings across the UK.
Unison general secretary Dave Prentis said: "We need imagination and vision to deliver real energy savings for the long term. It is pathetic that just 626 homes have completed installing energy efficient measures under the Government's Green Deal.
"Energy companies have a better track record but, using the conversion from town to natural gas as a blueprint, we could create energy-efficient homes across the whole country.
"We must stop the obscene amount of heat that goes out of our windows, doors and walls straight up into the atmosphere."
Brian Berry, chief executive of the Federation of Master Builders (FMB), said: "It's clear that the Green Deal simply has not achieved the desired results in its first full year, with the majority of small and medium sized enterprises (SME) installers and home owners failing to engage, and the financial package underpinning the scheme proving unattractive to most consumers."
He said the Green Deal did not work as a financial package in the face of many attractive high street alternatives, and other incentives such as a reduction in stamp duty for those taking up the programme were not inclusive.
He said: "The Government needs to accept that the Green Deal's first year has been underwhelming at best.
"The single most effective measure to kick-start demand would be to reduce the rate of VAT from 20% to 5% on all domestic repair and maintenance work, including energy-efficiency improvements.
"This would be a real incentive to home owners across the board to think about getting a professional tradesperson in to quote on a variety of repair and maintenance projects."