The procurator fiscal’s office in Elgin, Moray, has been closed for nine months to be fitted with the environmentally friendly technology.

The original cost was around £2.2m when the project was first announced in August. It has now been reported that the bill has increased by more than £1m in only a few months.

The Crown Office originally said: “The goal is to enable the office to further adopt renewable energy sources and at the same time cut costs to the public purse.

“The work, which is budgeted to cost £2.2 million, is part of a Scotland-wide commitment by the Crown Office and Procurator Fiscal Service (COPFS) estates strategy to drive towards utilising renewable energy.”

Fergus Ewing, a former SNP minister, told The Sunday Mail: “This fiscal fiasco is wasting millions of pounds which could be better spent. This is the price of having Green ministers in government.

“They impost their madcap schemes on normally sensible organisations like the Crown Office – though why they went along with this must be independently reviewed.”

A COPFS spokesman said: “We are committed to ensure value for public money in all contracts, which are subject to a robust and compliant procurement process.

“COPFS is also committed to meet its targets to reduce carbon emissions in COPFS premises by 2.5 per cent each year and become carbon neutral by 2040.”