The UK business secretary Sajid Javid has announced plans to partly-privatise the Edinburgh-based Green Investment Bank (GIB).

Speaking at the annual meeting of the UK government’s “green” bank, which invests in environmentally-friendly infrastructure projects, the minister said that he is to start “exploring options” to bring private investors into the world’s first dedicated green investment bank.

The pioneering project has invested about £2 billion of public money in about 50 projects with a total value of more than £8bn since its creation three years ago.

And results for the bank announced in April, show that the GIB, which started making profits in the year to March 31, invested £723 million in 22 new green-energy schemes, worth a total of £2.5bn in 2014-15 alone.

Its support ranged from a £1.5m investment in an anaerobic digestion plant in Northern Ireland to £6m for low energy street lighting in Glasgow and £240m for an offshore wind scheme off the Norfolk coast.

The bank’s chairman Lord Smith of Kelvin told yesterday’s gathering in London that the GIB has “established a successful business model” and played a key role in strengthening energy supply and security, while reducing energy demand and “decarbonising our economy”.

The GIB was launched with a pledge to provide loans to “green” projects that have also attracted private sector money, and critics have called plans for a sale “reckless”, and said that the move calls into question the government’s commitment to a low carbon economy.

The GIB says that for every £1 spent a further £3 is contributed by private sector investors.

But there are restrictions on its borrowing, and Mr Javid hopes that full access to the capital markets will increase its lending powers.

Mr Javid said that the bank “has shown that investment in green technologies can be a profitable business. The challenge now is to build on this success”.

He added: “The bank will still be green, still be profitable, still be a market leader in financing environmentally sound infrastructure. But free from limitations on where it can borrow money and EU regulations on state aid, the bank will be able to access a much greater volume of capital.”

Deputy first minister John Swinney urged the UK government to commit to maintaining a public stake in the bank, and to ensure it retains its original purpose as a green bank.

He is also calling for reassurances that the headquarters and jobs are retained in Edinburgh, and that all of the previously announced £3.8bn capital provided to the bank is carried through.

Mr Swinney said: “Continued investment in tackling climate change and reducing our carbon footprint is essential and I urge the UK government to provide guarantees on the future of the Green Investment Bank.

“The UK government must retain a public stake in the bank and the UK government must also ensure the Green Investment Bank’s headquarters and jobs are retained in Edinburgh, as it was specifically chosen to reflect Scotland’s position at the vanguard of the renewables sector.

“The original purpose of the bank, which was to accelerate the transition to a low carbon economy, must be retained. I am concerned that privatisation is seen as further evidence of the UK Government turning its back on green initiatives, particularly given their plans to cut support for onshore wind energy.

“I would also like reassurances that all of the £3.8bn funding announced for green projects in 2012 for the bank is honoured.”

Critics argue that a sale would dilute the bank’s purpose and undermine the UK’s commitment to the green economy.

Patrick Harvie, Scottish Green MSP for Glasgow and a member of Holyrood’s economy and energy committee said: “The sell-off of the Green Investment Bank proves that David Cameron’s comment about wanting to ‘cut the green crap’ has now become a full-blown mantra for a right-wing government determined to wreck our renewable energy opportunities. The bank was a half-hearted effort by the Tory-Libdem Coalition, with limited powers and funding. Rather than taking another backward step we need governments to go further and faster on developing new energy sources and cleaner industries as the need to leave fossil fuels in the ground becomes ever more urgent.”

Think-tank E3G, which advised on the original plans to established a green bank, said a sell-off would be “reckless” and damage investor confidence.

Chief executive Nick Mabey said: “The Green Investment Bank is not just the government’s most lauded innovation in the war against climate change. It has kept investment in the real economy going at a time when bank lending had fallen to an all-time low. It has played a critical role in supporting the UK economic recovery.”