SNP Cllr Alasdair Rankin also said that a referendum on whether to go ahead with the extension of the tram line to Newhaven should be “considered”, an e-mail from 2017 to a campaigner has found.
The council is set to approve extending the tram to Newhaven at a crunch meeting on Thursday.
But in an e-mail to anti-tram campaigner Douglas Thomson in April 2017, Cllr Rankin called for no decision to be taken until the Hardie inquiry into the first phase of the project has reported back.
The inquiry findings are still yet to be revealed.
In the e-mail, Cllr Rankin said: “I am clear that no decision can be made ahead of the full report from the tram inquiry.
“I feel sure that the council would not be so unwise as to make a decision to start a tram extension in June , but will at least wait until there has been time to consider the inquiry report fully.
“In my view, there needs to be an informed, public debate about whether or not an extension should be built.
“I think a referendum would certainly have to be considered, although there is a price tag attached.
“At the minimum, there does need to be that full, informed public debate.”
Conservative and Liberal Democrat councillors are refusing to back the extension plans, in part due to the Hardie inquiry findings not being published.
Responding to the e-mail, Cllr Rankin said: “The business case has taken account of those lessons learned from the post-mediation phase of the original tram project.
“The project was taken forward, after mediation, in a far more effective way.
“I am, of course, keenly aware of the extent of the failings and cost of the original tram project and I acknowledge that those issues remain prominent in many people’s minds whenever the subject of the tram comes up. I seriously considered the idea of a referendum because of my concerns about those very issues.
“However, I have moved, over time, from a position of instinctive opposition to an extension of the tram to positive acceptance of the case for going ahead. This is because of all the lessons learned and the extent and depth of the diligence and expertise that has been put into shaping the current proposal.”
Mr Thomson, who received the e-mail, is holding a protest outside City Chambers before the meeting on Thursday. He is urging others who oppose the extension to meet him at 9am in a “last ditch effort to show disapproval”.
He said: “There was a hell of a carry on last time with the utilities.
“The remit of the tram inquiry was to stop problems as well as future projects being mismanaged, but we are not going to get the report in time. That to me is almost beyond belief.”