George Osborne condemned as clean energy firms go into administration
The Government has been accused of "killing" jobs after two clean energy firms went into administration, hitting around 1,000 workers.
Home insulation firm the Mark Group and energy efficiency firm Climate Energy went into administration within hours of each other.
More than 900 jobs will be lost at Leicester-based Mark Group, which has cancelled all surveys and installations.
A skeleton staff has been retained by administrators.
Climate Energy, a provider of "energy efficiency solutions", posted a notice on its website saying it has gone into administration.
Greenpeace said Government policies were killing jobs.
Its UK chief scientist Dr Doug Parr said: "For all his rhetoric about building, it's not scaffolding George Osborne is bringing to Britain's clean energy sector but a wrecking ball.
"Evidence is growing that the Chancellor's policies are putting people out of jobs, damaging investment, and harming one of the country's most promising industries.
"This should be a wake-up call for David Cameron, who faces international embarrassment ahead of crucial climate talks. As Prime Minister, he has a duty to leave internal party politics aside and rein back a rogue Chancellor who's putting investment, jobs, and growth at risk."
Friends of the Earth energy campaigner Alasdair Cameron said: "These huge job losses are likely to be the first of many as Government attacks on efforts to build a low-carbon economy begin to bite.
"Government policy threatens over 20,000 UK solar jobs - with many more at risk in other green sectors.
"It seems the Treasury is happier to give sky-high subsidies to Chinese nuclear power than support British solar.
"The renewable energy industry around the world is booming and costs are falling rapidly but the UK government seems to be stuck in the wrong century."
Andrew Cooper, the Green Party's energy spokesman, said: "Only last week the Government unveiled an £80 million package of training and support to establish new businesses for 1,700 staff who lost their jobs when the SSI steelworks at Redcar lost their jobs when the company SSI went into liquidation.
"Over 1,000 jobs are now at risk in the energy efficiency industry. This is a direct result of the Government's abandonment of green policies so it bears a heavy responsibility for the loss of those jobs. Greens are calling for an equivalent package for staff losing their jobs in the energy efficiency sector.
"Of course the sensible thing would be for Government to have consistent policies that promote insulation and small-scale renewable energy installations but, while we wait in hope for Government to realise this, we need support now for workers who have lost their jobs."
Lisa Nandy, shadow energy and climate change secretary, said: "Mark Group and Climate Energy going into administration with the loss of nearly 1,000 jobs is a devastating cut for our clean energy industry in the UK.
"This government's recent raft of decisions to roll back solar and wind programmes and to instead direct subsidies towards more expensive energy technologies shows the hypocrisy of their claims to be protecting bill payers.
"Not only could these decisions put up household fuel bills, they are already causing job losses in an industry with the potential to be a new powerhouse for Britain.
"The Chancellor should heed the warnings from the CBI and others about the damage he is doing to investment confidence at a time when we face the prospect of an energy security crisis."