Those singled out by inquiry chairman Lord Hardie among some 90 witnesses who gave oral evidence to the hearings will have until December 2 to respond to the criticism, which he will consider before completing his findings.
The news has led to speculation the former judge might seek to publish his report into the massively delayed and over-budget project by Christmas, or before the tram line extension to Newhaven is opened around June next year.
One of those who received a letter told The Scotsman they expected “a lot” of others to be issued. Letters are understood to have been sent to several former Edinburgh city councillors, and senior officials of the council and its former tram firm Tie.
The final stages of the inquiry come eight years after it was announced by then first minister Alex Salmond and four-and-a-half years after its eight months of public hearings ended. It is expected to cost more than £13 million.
In a statement, the inquiry said: “Lord Hardie has issued warning letters relating to his report into the trams project. He has informed recipients that if they wish to respond, the response must be received by the inquiry no later than 5pm on Friday, December 2. His report will be finalised after all responses have been received and considered.”
An inquiry spokesperson added: “In line with the Inquiries (Scotland) Rules 2007, Lord Hardie has issued letters to parties who are subject to criticism in the inquiry’s report to allow them the opportunity to respond. This is standard procedure as the inquiry works towards producing the report and recommendations, which will be published as soon as practicable.”
Iain Whyte, the city council’s opposition Conservative group leader, said: “It is good news the tram inquiry finally seems near to issuing a report as it has been churning through taxpayers’ money at the rate of hundreds of thousands of pounds a year while the public have had to wait for an outcome. That warning letters have been sent out with a fairly short deadline for response suggests there is finally a sense of urgency to issue the report.
"It is imperative that any further process after the December 2 deadline is short or we could see the farce of the completion of the section to Newhaven being up and running before we even have the report into what went wrong with the first tram project.”
The council’s Labour leader Cammy Day said: “This is long overdue and at a huge cost to the public purse. I hope these letters indicate the inquiry is now coming to an end and we can learn from the past.”.
Former council Labour leader Donald Anderson said: "If the inquiry is moving towards a conclusion, I'd be delighted. It's been a long time coming and I do hope it gets to the facts about what went wrong and draws robust conclusions about how to avoid such mistakes in future.
"As for the trams, they're carrying way more passengers than could have been predicted for a partially delivered route and I'm sure will carry hundreds of thousands more when the extension is complete."