The chief executive of the UK Infrastructure Bank has called on investors to reconsider their approach to risk appraisal and commit more funds to the race to net zero.

John Flint, who will oversee the distribution of £22bn of public money to support infrastructure projects over the next eight years, admitted the country was "in a bit of a funk" due to adverse economic conditions.

But he said the UK had a clear strategy to get to net zero and a government with a "track record of delivery".

He called on private investors to play their part by "challenging return expectations" and taking a longer-term view of the value of sustainable infrastructure.

If they did, he said, the UK Infrastructure Bank stood ready to help, adding: "The money is there."

John Flint said the bank had so far committed just £2bn of the £22bn it was making available. But he admitted that even £22bn was a "tiny" amount in the context of the total spend that would be necessary to achieve net zero - and beyond.

What was missing, he said, was the "quantum of private finance" needed to effect permanent and rapid change.

John Flint called on potential private investors to meet the bank halfway in terms of the returns they expected from green infrastructure projects.

He was taking at a panel session in the Beyond Net Zero pavilion at UKREiiF, mediated by UKBCSD chairman Jason Longhurst.

The pavilion, whose sponsors include UKBCSD, has invited a string of high-profile public and private sector leaders to address key questions around the energy transition and sustainability.

John Flint was joined in his mid-morning session by Catherine Raw, MD of SSE Thermal; Andrew Farrimond, Infrastructure Sector Lead at Aviva Capital Partners; and Shavran Joshi, chair of planning at the City of London Corporation.

The late afternoon session, chaired by Tim Newns, Managing Director for Levelling Up at the Office for Investment, looked at the challenges and opportunities presented by the energy transition for real estate and the wider built environment.

Speakers included Simon Cox, senior VP and Head of Project Management at Prologis; Luba Nikulina, Chief Strategy Officer at IFM Investors; Alexa Culver, General Counsel at the Environment Bank; and Jules Pipe, London's Deputy Mayor for Planning, Regeneration, and Skills.

The panel discussed critical issues including the limitations of the National Grid; the need to reform planning regulations in a way that encouraged development using sustainable materials and techniques; and the growing recognition that biodiversity was a critical factor in sustainable development.

The afternoon started with a session on driving potential in sustainable infrastructure.

The session was moderated by CBRE director Claire Weir and the panel included Simon Cox; Grant Findlay, board member at Sir Robert McAlpine; Joanne Patrick, Head of Sustainable Energy at Amber Infrastructure Group; and Xavier Brice, CEO of Sustrans.

Joanne Patrick stressed that investors were increasingly demanding higher standards of accountability, adding: "Gone are the days when you could greenwash".

She told delegates: "Investors getting more clever in their due diligence.

"They are looking for the industries that sit behind the construction industry to show they are also decarbonising."

Grant Findlay called for more collaboration and partnership in promoting sustainability solutions.

He said: "Partnership for me is a much more collaborative approach to how we solve the big issues

"One of the things that has caused the slow pace of doing better on sustainability is that for a long time we thought it could be a competitive advantage.

"We should be democratising those things that we think are solutions to lift all the boats, so that we are all doing better all the time.

"There is real value in collaboration."

In the final session of the day, Matthew Dowdeswell and Dr Harriet Kildahl of Inspired Plc talked about how new and existing buildings could be shaped to help achieve net zero.

They mentioned five key challenges in retrofitting existing buildings - which will make up 80 percent of all stock by 2050 - which were: data, planning, finance, implementation, and building users.