Four million solar panels covering land the size of 3,400 football pitches should be built on government land and property including schools and prisons, a minister will announce.
Greg Barker, the energy minister, is expected to in the New Year disclose plans for one gigawatt of electricity generated by solar panels on the “government estate”.
It could mean huge solar farms on Government land as well as panels on thousands of public buildings.
Mr Barker's desire to dramatically increase the Government's commitment to renewable energy will dismay many senior Conservatives.
The plans are understood to be a “personal ambition” of Mr Barker’s and are not an official Government target.
Mr Cameron was earlier this year forced to respond to claims he told aides to get rid of the "green crap" from energy bills.
It was claimed he was referring to green subsidies that help to fund wind power, solar panels and other renewable energy schemes.
In a speech earlier this month, Mr Barker said: “We need to make the Government itself a leader in solar deployment.
“Government public buildings should be at the forefront of the move to renewable energy.”
He added: “So next year you can expect to hear more from me on my ambitious plans to ensure the government estate plays its part in the decentralised energy revolution.
“The Government is sitting on huge potential; we need to do much more.”
The Solar Trade Association said that one gigawatt of solar would equate to about four million panels.
Its land use estimates suggest that if these were deployed as solar farms it would require up to 6,000 acres of land – the equivalent of 3,400 football pitches.
The Ministry of Defence is one of Britain’s largest landowners, creating the potential for solar farms to be built on its land.
School and hospital roofs could also be potential sites.
Typically power from a solar farm is fed into the electricity grid, whereas power generated by panels on roofs can first be used to power the building itself.
All types of solar projects currently receive subsidies paid for through levies on consumer energy bills.
Mr Barker has said his “ambition” is for Britain to have 22 gigawatts of solar power installed by 2020. The Solar Trade Association says one-third of this could come from installations on domestic roofs, one third on large buildings like commercial sites, and one third in solar farms.
But official government documents suggest that there would actually be far fewer farms, with between 2.4 GW and 4 GW of “large-scale” solar developments such as solar farms.
Solar farms have proved hugely controversial, with Eric Pickles, the communities secretary, intervening to block a proposal for one of Britain’s largest solar farms in Suffolk.
Critics also raise fears about agricultural land being turned over to solar farm use.
But the STA argues that even if 10GW was deployed, it would amount to 0.1 per cent of UK land, which it says is less than is used for non-food crops like linseed, or landfill sites.
Leonie Greene of the Solar Trade Association said: “Solar farms have an important role to play delivering green power at low cost. Done well solar farms can also actively help boost British biodiversity by providing wildlife sancturies. Only 5 per cent of the land a solar farm is on is taken up with fixings, so 95 per cent of the land remains available to other uses. The solar industry is moving to make sure much of that land is used to help our threatened flora and fauna."
The STA argues there are not enough large-scale solar roof installations taking place. “Potential output is vast and this is a very cost-effective and efficient way to deliver solar power - right at the point of use,” Ms Greene said.
There is no fixed timetable for the implementation of Mr Barker’s plans, it is understood.
A Downing Street spokesman said: “We said in the Coalition Agreement that we would take measures to improve energy efficiency in public sector buildings. We have already taken steps to achieve this in Downing Street and across the Government estate and this work is ongoing.”
Andrew Pendleton, Friends of the Earth's head of campaigns, said: "Turning government land and buildings into a myriad of mini-power stations is a fantastic idea and will enjoy lots of support.
"By helping schools, communities and offices to become generators of their own power, we can escape the grasp of the greedy Big Six energy companies and beat climate change.
"But ministers can and must go further and create the right climate for investors large and small to develop the UK's massive renewable power potential."
16 Jan 2014 The Telegraph