The club's money problems have shown little sign of improving this season, and Clark has revealed that he will not be able to sign new players in the January transfer window unless current members of his squad depart St Andrew's.
The 41-year-old told the Birmingham Mail: "There will be nothing happening. It will be very similar to last January in terms of people having to be moved out before players are brought in.
"That's the situation now. It doesn't matter if it changes because of injuries or suspensions, that's the position that we are in financially.
"I fully understand it and I'm aware of it so unless we move any players on to make way for new arrivals, we will have to make do with what we've got."
Birmingham are currently two points clear of the relegation zone.