Solar installations completed before 3 March will attract the higher 43p per KWh rate

The Supreme Court has rejected the government’s appeal over an earlier high court ruling that its timetable for cuts to the solar feed-in-tariff was illegal.

The government announced plans to slash the feed-in-tariff for installations made after 12 December 2011 in October last year.

However, its consultation on the decision did not close until 23 December, which allowed Friends of the Earth and solar firms to successfully appeal to a high court judge to strike down the cut-off date as retrospective and illegal.

The Department for Energy and Climate Change (DECC) subsequently applied to appeal the ruling at the Court of Appeal but that court denied it permission to appeal and upheld the High Court’s decision.

Now the Supreme Court has also refused to hear the case.

Energy secretary Ed Davey said he was “disappointed” by the decision but that it “draws a line under the case”.

He added: “We will now focus all our efforts on ensuring the future stability and cost effectiveness of solar and other microgeneration technologies for the many, not the few.”

Andy Atkins, executive director of Friends of the Earth which brought the case along with a number of solar firms, said: “This is the third court that’s ruled that botched Government solar plans are illegal - a landmark decision which will prevent ministers causing industry chaos with similar subsidy cuts in future.”

Jeremy Leggett, chair of Solarcentury, one of the solar firms which brought the case, said: “I hope the government is now clear that it will be held to account if it tries to act illegally and push through unlawful policy changes. We would much prefer not to have taken this path but ministers gave us no choice.”

Paul Barwell, chief executive of the Solar Trade Association, said: “The extra money DECC will now have to commit leaves us with serious concerns about the remaining FIT budget, which remains constrained under the Levy Control Framework.”

He said he feared firms would go under if the industry was not given enough support.

Caroline Flint, shadow energy secretary, said the ruling showed the “chaos and incompetence at the heart of DECC”.

“For months, it’s been the same old story: broken promises on the environment; and Liberal Democrats propping up a Tory-led Government doing the wrong thing for the economy and the wrong thing for the future of Britain,” she said.

The government has already passed secondary legislation to bring about the cut in the FIT from 43p per KWh to 21p per KWh from 3 March, which is not in dispute.