The I-League Core Committee of the All India Football Federation (AIFF) ruled that the Kolkata giants had breached the rules by refusing to return to the pitch following an outbreak of violence during the first half of the derby match against East Bengal in early December.
Mohun Bagan had pleaded that their non-reappearance for the start of the second period was, in reality, due to exceptional circumstances and should not, therefore, be considered a contravention of any I-League regulation.
The Core Committee however agreed with the report submitted by the Honourable Justice A K Ganguly, who had concluded that Mohun Bagan's actions were a flagrant breach of the regulations - a transgression which carries an automatic suspension from the I-League and the possibility of a further two-year ban.
It was also decreed that all games already played by Mohun Bagan in the 2012-13 I-League season are to deemed null and void.
A further meeting to finalise matters is scheduled to be held in the Indian capital of New Delhi on January 9 when representatives from Mohun Bagan are expected to be present.