The 90% cut to staff budgets faced by the Department of Energy and Climate Change (DECC) could jeopardise its ability to reach green goals.
The findings, by politically-neutral environmental think tank the Green Alliance, estimated once officially and unofficially protected spending was taken into account cuts would leave the department with just £40m by 2018-19.
This is for ‘resource spending’, which largely consists of staff costs. That budget is £402m in 2014-15.
Speaking to the press former energy secretary Ed Davey said cutting DECC’s head count would damage economic growth and undermine private investment.
Ring-fencing of health, education and development budgets means other departments face an average cut of 11.6% over the next five years, with the steepest cuts expected at the start of the parliament.
Matthew Spencer, Green Alliance’s director said: “You have to have internal expertise, you have to have some troops in the department able to interpret ministers’ words.”
“If you end up with a dumbed-down department you get a bad deal for consumers and citizens.”
Mr Davey said: “The main effect of slashing the headcount at DECC will be cutting economic growth and undermining private sector investment.
“It is ‘Osbornomics’ at its worst.”
He added the department was an “economic powerhouse” for the UK, with energy infrastructure investment dwarfing investments in transport, communications and water combined.