The UK government has come under heavy criticism from the Liberal Democrats and the Greens after it confirmed the sale of the Edinburgh-headquartered Green Investment Bank (GIB) on Friday 18 August.
Australian investment bank Macquarie Group Limited has acquired GIB, which will now be know as the Green Investment Group (GIG).
The sale of the institution, which employs 135 people, has been branded "environmentally irresponsible" by former business secretary and current Lib Dem leader Sir Vince Cable.
"The Bank has done an extremely good job in supporting renewable energy, energy efficiency and low-carbon projects. It has managed to attract over £10bn of private investment in these sectors that would not otherwise have happened," he said.
"At a time when business confidence is falling and the Conservatives are giving mixed signals on their commitment to the environment, this is the worst time to undermine investment in the green economy.
"The Green Investment Bank's environmental mission is in danger of disappearing under the ownership of a private Australian bank whose track record does not inspire confidence."
Jonathan Bartley, co-leader of the Greens, also criticised the government over the move.
"The government was repeatedly warned that selling the GIB to Macquarie could result in asset-stripping and leave the bank unfit for purpose," he said. "The sale means taxpayers no longer have a say if this turns out to be true.
"As we grapple with soaring temperatures and a climate change denier in the White House we need to be investing in green energy, not flogging off our future security to the highest bidder."
But Claire Perry, the Conservative climate change minister, said the acquisition means that all the taxpayer funding invested in GIB since its creation in 2012 has been returned, with a gain of £186m.
"We led the world in setting up the Green Investment Bank and it is now being copied by others," Perry said.
"Now that it's in the private sector, it will be able to operate on an international level to tackle the global challenge of climate change. It is also perfectly placed to help us finance green initiatives for our Clean Growth Plan and realise the commitments set out in the Paris Agreement."