Under its new ownership, the GIB will look to invest at least £3bn of new investment into the green economy over the next three years.

The acquisition follows the launch of a sale process by the government last year.

“The Green Investment Bank has been very successful in attracting private capital to the UK's green economy,” said Nick Hurd, climate change and industry minister.

“It now makes sense to move it into the private sector where it will be free from the constraints of public sector ownership, allowing it to build further on its success.

“GIB has a well-funded new owner that is committed to the bank's green mission, with a track record of success in green investment and an ambition to grow the business.”

GIB will become the primary vehicle for Macquarie's renewable energy investment in the UK and Europe.

The group has pledged to maintain the GIB's green purpose, utilise the skills of GIB employees in Edinburgh and London and create a new revenue-generating project delivery business to provide services for its green energy portfolios in the UK.

Meanwhile, all taxpayer funding invested in the GIB since its creation in 2012, including set-up costs, has now been returned with a profit.

As part of the transaction, a number of GIB assets will be moved into a new offshore wind investment vehicle managed by the bank, which will retain a 25% stake.

The government will continue to hold a £130m portfolio of a small number of GIB's existing green infrastructure investments, which will continue to be managed by GIB until they are sold.

“There is a compelling logic in the world's first green bank joining forces with the world's largest infrastructure investor,” added Lord Smith of Kelvin, independent chair of GIB.

“When we embarked on this process, we were determined to find a new owner who would build on GIB's successful history –  an owner who would have access to deep pools of capital, a commitment to expand GIB's activities, and a respect for the unique role GIB has played in the market.

“Macquarie will bring all of this to GIB, along with its own impressive track record of green investments.”

Macquarie and its managed funds have invested or arranged more than £8.5bn of capital into green projects since 2010.