Coventry's city centre management company is urging the council to come up with the £21m loan needed to save a £113m football stadium project.
Coventry City are scheduled to play at the Arena from 2005
The 32,000-seat Coventry Arena scheme has been plagued with difficulties from the start, with the latest setback being the withdrawal of a major financial backer last month.
The directors of management company CV One are now calling for city councillors to help finance the multi-purpose complex in Foleshill when they vote on 16 October.
CV One says that, if the authority does not come up with the £21m, "major damage" would be inflicted on Coventry's economy and image.
The management company heard at a meeting on Tuesday the city is already losing about £1m a year because it does not have conferencing facilities capable of accommodating at least 1,000 people.
The Arena project is planned as a multi-purpose complex, with dining and conference facilities, a music venue, a hotel and a casino, as well as being the new home of Coventry City Football Club.
CV One said it fears if the authority does not help out, all that would be left of the scheme would be a Tesco superstore.
The company also said that the failure to complete the project in full would leave the impression Coventry is a place where large-scale developments cannot happen.
CV One chairman Martin Ritchley, who is also chief executive of Coventry Building Society, said: "We have to consider the wider interests of Coventry as a whole.
"That's why we have supported the Arena project because it offers enormous economic and social benefits to the city.
"We are unanimous in calling for councillors to back it now at this critical moment."
Liz Millett, CV One's chief executive, added, "The Arena project is absolutely vital to Coventry's future.
"If we pull out now, the consequences will be disastrous and our credibility as a city will be hugely damaged."