THE cost of Edinburgh’s controversial tram inquiry is rising at a rate of around £100,000 a month, according to the latest figures.
Officials have revealed the overall cost of the probe, which is currently holding public hearings, has now reached £7.2 million.
In September it stood at £6.9m -- with the majority of the cash going towards staff costs and “professional fees”.
It comes as former tram boss David MacKay said Edinburgh could have become “the laughing stock of Scotland, if not the world” had disputes not been resolved during the project.
Scottish Conservative MSP Miles Briggs said people had “understandably lost patience” with the inquiry.
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He added they “deserve answers on why it is taking such a length of time and why it is costing so much taxpayers’ money”.
He said: “Much like the trams project itself, the costs of this process seem to be spiralling out of control and local residents are increasingly concerned and angry.”
The tram inquiry was set up more than three years ago under Lord Hardie, the former lord advocate, but only started hearing oral evidence in September.
When former First Minister Alex Salmond announced the inquiry in 2014, he promised it would be “swift and thorough”.
But more than six million documents are being examined as part of the probe and it will not hold anybody legally responsible or financially liable.
Figures released at that time showed costs rocketed by almost £1m in the space of three weeks as witnesses began giving evidence in person.
Edinburgh’s tram line opened in 2014, three years late, substantially reduced in scope and £231m over budget.
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A spokesman for Transport Scotland said Government ministers “have no role in the day-to-day running of this inquiry”.
But he added: “They want it to be efficient, cost effective and deliver clear recommendations for the planning and construction of any future major tram and light rail projects of a similar nature.”
It is believed Lord Hardie will hear oral evidence until the end of the year.
Evidence given to the inquiry will then be reviewed before an official report is compiled, which could take several months to complete.
A spokesman for the Edinburgh Tram Inquiry said: “All efforts are being made to ensure the Inquiry delivers best value for the public purse.”