A councillor is demanding the City of Sydney cancel the controversial Cloud Arch public art project if the current multi-million-dollar budget blows out any further, as new potential cost issues emerge.

The $11.3 million steel ribbon sculpture, set to span 58 metres across George Street and referred to by one councillor as "a big tapeworm", received final council approval just under a year ago.

But councillor Kerryn Phelps will move a notice of motion at Monday's council meeting, seeking an assurance that the project will be abandoned should the cost increase.

The original contract estimate in 2014 was about $2.5 million dollars — nearly five times less than the current price tag.

"I'm looking for a guarantee from council that if this project exceeds $11.3 million, which is the current budget of the estimate, that it will be cancelled," Councillor Phelps said.

"I don't believe that the ratepayers of Sydney are willing to pay this sort of money for a public artwork which has, at the moment, what appears to be a blue-sky budget."

The councillor's demands come after reports of a separate development application (DA) lodged for lighting the structure.

The 58-metre sculpture, by Junya Ishigami, was announced on July 29, 2014. ( Sydney City Council )

Councillor Phelps says the DA has not been exhibited publicly and is being dealt with by the local planning panel.

She has questioned the implications of lighting the arch, including the power source and environmental impact.

"We're told that solar is not an appropriate power source for this, so what is the power source?" she said.

"These are the questions the people of Sydney want to know before this project gets underway."

It is unclear if the illumination of the structure would increase the overall cost of the project.

A spokesperson for Lord Mayor Clover Moore said the cost of the project would not change.

Cloud Arch was designed by Japanese artist and architect Junya Ishigami.

The project is due to be completed before March 2019 but construction is yet to start.