Birmingham finished 10th in the Premiership last season

Sullivan and the Gold brothers, David and Ralph, have pumped millions into Blues since they saved them from the threat of liquidation 11 years ago.

"Not a single person from Birmingham in 11 years has come forward," Sullivan told the club's official magazine.

"There are some multi-millionaires in Birmingham but do they want to give anything back to the city or the club?"

Sullivan added: "If they do, we'd love to hear from them.

"It is still hard to believe that, given the size of Birmingham and the business community, there is no-one out there who could help.

"People, companies and rich private individuals won't part with their money. It is very frustrating."

We wrote to the Thai government and said 'if you don't make it with Fulham or Liverpool please come to us' Birmingham co-owner David Sullivan

City are keen to secure additional investment in an attempt to consolidate their Premiership status and challenge for European football.

Sullivan revealed that he had written to the government in Thailand, who have had discussions with Liverpool over possible investment.

"We'd love to get some investment from the Far East. We have always had an open-door policy," he confirmed.

"Something like that would enable us to improve the club's infrastructure, also help squad strengthening as well as help promote us in new markets.

"We actually wrote to the Thai government and said 'if you don't make it with Fulham or Liverpool please come to us and we'll give you a better deal'.

"But we never got a reply. We would welcome that sort of investment from anybody to share the load."

Sullivan stated: "The potential is here and we've got to a level where finishing sixth in the Premier League would be a very successful year.

"I cannot see how it can get higher than that without an influx of Russian money, Far East money or something like that."