The £10 million costs of a Centenary Square revamp must not be allowed to spiral out of control, nor the project over run, a council watchdog committee has warned.
The corporate resources committee issued the stern warning to Labour cabinet members Stewart Stacey and Tahir Ali, who are fronting the plan to completely redesign one of the city's premier public spaces.
There are fears lessons were not learned from the Golden Square project in the Jewellery Quarter which was delivered 50 per cent over budget.
But the committee stopped short of putting a formal brake on the policy after being given assurances it would be kept updated throughout the two-year development.
The £10 million contract was for a firm to finalise details of the Column of Light design for the square and then see it built by summer 2018 - in time for the World Indoor Athletics Championships.
Coun Jon Hunt (Lib Dem Perry Barr) raised concerns the contract was awarded on the basis of quality and without consideration to costs, adding that only two companies applied.
He said: "There is a lack of clarity on how costs can be managed or contained."
There were questions from across the committee on who would foot the bill if it ran over and what penalties or incentives there were for delivering it on time.
Coun Stacey (Lab Acocks Green) replied that the contract had been agreed on a new system set up by the Government to better manage costs.
He said companies had already gone through a first tender stage to get on an approved list before they were able to bid for the contract which was why only two eventually came forward.
"There was competition. If there had only been one bidder I would have started again," he said.
He added the tight timescale played a part in narrowing the field.
Designs are being finalised now ready for planning permission to be sought with construction due to begin in January.