A bidding process has been started under which the government is planning to sell 75% to 100% of the institution.
The deal will include the sale of government-owned shares and the commitment of additional capital for GIB by new investors.
The deal is expected to be completed by the end of this year.
GIB primarily invest in energy efficiency, waste and bioenergy, offshore wind, and onshore renewables.
The bank has made £2.6bn in investments into 70 green infrastructure projects throughout the UK.
GIB independent chairman Lord Smith of Kelvin said: "Attracting new investors is vital if GIB is to fund its ambitious plans to double the size of its business, expand into new parts of the UK green economy and deliver a growing green impact.
"This launch, and the wider plans to introduce new capital and new owners to GIB, has the full support of GIB’s independent Board."
Plans to make the GIB private were initially unveiled in June 2015, when UK Chancellor George Osborne said a privatization would help the bank get more capital to invest in a range of green sectors.
GIB is wholly owned by HM Government. The company is not authorized or regulated by the Financial Conduct Authority or the Prudential Regulation Authority.
A subsidiary UK Green Investment Bank Financial Services, is authorized and regulated by the Financial Conduct Authority.
Image: In May 2015, Prime Minister David Cameron visited the UK Green Investment Bank headquarters in Edinburgh. Photo: courtesy of UK Green Investment Bank.
