The Serbian has scored five goals in 16 Championship appearances for Birmingham this season and has been the subject of an offer from Spanish second division side Villarreal.
The 32-year-old's representative Milan Calasan also claims several other clubs have shown an interest, but that Zigic is in no hurry to quit St Andrew's.
"The Spanish club offered 50 per cent of Zigic's salary, but they want Birmingham City to pay the other half of his contract," Calasan told Sport.
"But Nikola is staying, he is not moving to Villarreal. He is not interested in moving to the Segunda Division, he is now waiting for a better opportunity.
"And there is something else - his kids are in school in England, that's why he is not so keen on moving in January. And he also loves England, more than he loved Spain.
"He is happy with the money he gets, he loves life in the UK. He has a contract as though he would be playing for Manchester United.
"Birmingham City could buy five new players if he were to move but, as I said, he is not really keen on moving right now.
"But there are clubs interested in him. Not only Villarreal, but also clubs from Germany and Asia, Levante, Malaga, there was interest from West Ham United and Newcastle United and so on."