SENIOR officials involved in Edinburgh's troubled trams project face the prospect of being held to account after First Minister Alex Salmond backed calls for a public inquiry.

Mr Salmond told the Scottish Parliament such a move would allow planners and politicians to be questioned over how the price was allowed to run out of control. The cost of abandoning it was put at £750 million.

Yesterday, Edinburgh City Council published a crucial report outlining the estimated costs of the various options for the future of the project.

Officials urged councillors, who will meet next week to discuss the project's future, to opt for the most expensive proposal which is to run trams from Edinburgh Airport to the city's St Andrews Square at a cost of £773m.

At First Minister's Questions, Mr Salmond said: "I think we should let Edinburgh Council continue its deliberations. But I think a public inquiry would be an excellent thing to do."

Kezia Dugdale, the Labour MSP for Lothian, had raised the issues with him.

She said: "A full, independent public inquiry is the only way we can get to the bottom of exactly how the project has been allowed to go so badly wrong.

"This is now about making the best of a bad situation and I look forward to working constructively with the Scottish Government to get the inquiry up and running as soon as possible."

Among those who could expect to face a grilling is Richard Jeffrey who recently stood down as chief executive of the trams company, Tie.

The Scottish Government has said it will not give any more than its original £500m pledge.

Council leader Jenny Dawe said: "This report is crucial for the tram project. The options presented give elected members a lot to think about in deciding the future of integrated transport for the city.

"Nobody would have wished for the problems that have beset the scheme. However, we must find a way forward that sees trams running on our streets in the next couple of years."

Ending the line at Haymarket would not make any money and the tram would need to be sub-sidised, while cancelling would cost 500 construction and 150 tramworkers' jobs.

The scheme was supposed to cost £545m, with £45m input from the council. So far £461m has been spent, and the council has put in around £17m.

The council said more grant funding would be cheaper than approaching alternative private sector backers who would seek a return for any a stake.

It emerged that £80m had been spent on project management and the cost of preparing utilities such as electricity cables and gas pipes had nearly quadrupled to £70m.

A source close to the project told The Herald: "The extra costs will include the costs of the disastrous strategy pursued by the former management of Tie.

"It also includes £80m spent on administering Tie, and that is an organisation that is effectively being wound up now.

"There were numerous faceless people there on six-figure salaries."

Sue Bruce, council chief executive, said: "We will be working closely with the Scottish Government in coming months to look at the various funding options."