Ngog was branded a cheat by Blues midfielder Lee Carsley for going down in the box without any contact from his challenge.
The 21-year-old has come under fire from a number of figures in the game, but Ngog's agent, Bruno Satin says the player is no cheat.
"He wouldn't try and con the ref," Satin told The Sun.
"He's a lad with very good education, correct and polite. He doesn't look for these things. He's never had a problem of this type before in his career.
"Maybe he fell down because he was worried about being injured. At times, players make very hard challenges in England. They allow a lot of things to defenders in the Premier League. At times it's really on the limit.
"Sometimes there are challenges that can assassinate you. A defender could get five matches for throwing his shirt and the player who broke the leg of Eduardo only had a three-game suspension.
"Did the defender put the safety of the player in danger? You have to look at things in a more reasonable proportion."
Meanwhile, Birmingham defender Scott Dann has called on the FA to punish any divers.
Dann believes players who con referees need to be suspended and he admits Ngog's actions were hard to take.
"The only way you can stop it is to suspend cheats and it's up to the FA to sort it out," said Dann.
"We all know diving goes on but no one likes to see it. I'd never dive to win a penalty.
"David Ngog is not the only one who has ever done it. A lot of it goes on and it is disappointing. It is a tough one for us to get our heads around.
"People say they are not sure what can be done to stop it, but rules can be changed to clean up football - and people have to be punished heavily.
"Everyone who saw it knew it was a dive. I am just sick because I had family and friends there and wanted to put one over on Liverpool.
"But we can take some consolation in the fact that Ngog had to dive to stop us beating them."