The economics behind George Osborne’s decision to make cuts to a series of green policies are “bonkers”, former energy and climate change secretary Ed Davey has told the Guardian.

In his first interview since losing his seat at the election, Davey said he struggled to comprehend the logic behind cuts to energy efficiency programmes and renewable energy incentives.

“What is frightening is that, despite all that success in low-carbon energy infrastructure, [Osborne] is prepared to send those disastrous signals. It was bad enough in the coalition when they were sending mixed signals but now there is no 'mixed' about it,” he told the paper.

“This is another thing I don’t get about Osborne’s economics,” he said. “They are really bonkers. The vast majority of this investment is private sector. Compare that with roads or railways or flood defences where it’s always the taxpayer.

“We battled every day. There were some Conservatives who were supportive like Greg Barker and Charles Hendry but they were a minority and the push was against the green agenda,” he added.

Since the majority Conservative government came to power cuts have been made to large-scale solar support and onshore wind incentives, the Green Deal has been scrapped and the Zero Carbon Homes policy severely hamstrung. Proposals to slash the feed-in tariff for solar by 87% have been described as “unnecessary, unjustifiable, unmanageable and ultimately destructive”.