Edinburgh's controversial Christmas Market did not have planning permission to operate last year, it has emerged.
Underbelly are still awaiting planning permission to operate in 2019/20, and still need a crucial building warrant.
The council said the market would not go ahead as planned on Saturday if the warrant was refused.
It comes after safety fears were raised over the scaffolding which supports a platform that will house the market in Princes Street Gardens.
The council is also investigating Underbelly's contract extension.
Planning permission is being applied for retrospectively and is expected to be granted by the time the Christmas Market closes in January.
Underbelly's approved planning application expired on 10 January 2018 - no application was made to renew the consent in time for last year's event.
Organisers earlier said they were "acutely aware" of this year's controversy.
Council leader Adam McVey said he had asked Underbelly's chief executive to get to the bottom of the issue "as a matter of urgency" and to ensure there were no repeats in future.
He said: "I'm extremely disappointed that Underbelly did not apply for the proper consents for Christmas 2018/19 as it was their responsibility to do so under the contract.
"That said, there are clearly lessons to be learned for our own processes both in terms of contract management and enforcement."
He added that the council's building standards and public safety teams were carrying out final inspections and checks of the site before it was expected to open.
A spokesperson for Underbelly said: "We look forward to the inquiry that councillor McVey has asked for and to contributing fully to the reasons why we are in the position we are now in.
"Our previous planning permission ran for four years but expired in January 2018; and we operated under the same conditions as applied for in the previous year.
"With the new arrangement in place, agreed by the council on 12 October, we are in the process of applying for the next planning consent."
Mr McVey said: "We've also recommended and approved pedestrian-only access on Waverley Bridge from 11:00 to 17:00 on Saturdays and Sundays to make it much easier for everyone to move around in a relaxed, fun and welcoming atmosphere."
The council has also launched an internal investigation into whether the correct processes were followed in handing over a two-year contract extension to the operator.
Edinburgh City Council's culture and communities committee considered a motion by Green councillor Alex Staniforth, calling to "urgently collaborate" with Underbelly.
It called on the parties "to look at options" for relocating this year's event to a hard-standing location in central Edinburgh.
However, councillors instead agreed a Conservative amendment, which would require officials to draw up options for next year's event - including moving the market.