According to BBC Scotland, the cost of the inquiry into the Edinburgh trams project, which went way over budget and was completed five years later than planned, has passed £3.7 million.

The inquiry was set up in June 2014 by then First Minister Alex Salmond, who said it would be “swift”, but Lord Hardie, who is leading it, has said he is unsure when he will be able to report his findings. A total of £1.822 million has been spent on staffing costs, while legal fees have cost £716,000.

A Scottish Assembly spokesman said: “Lord Hardie and his team are firmly committed to discerning the facts, and we have been clear from the outset that the inquiry should be efficient and cost-effective.”

The project was first mooted in 2003, when the Labour-led Scottish Assembly proposed building a network of tram lines by 2009 at a cost of £375 million.

The SNP minority government elected in 2007 wanted to scrap the project but the other parties in the Scottish Parliament voted in favour of going ahead. By the time the first trams started running on the 8.7-mile route in May 2014, the total cost of the project had reached £776 million.