The 2015 champions suffered the most shocking defeat of the season, going down to Gokulam Kerala FC 1-2 yesterday, a win that lifted the debutants from the bottom place.
The loss meant Mohun Bagan's title hopes were all but over with an eight-point gap to bridge against leaders Minerva and four matches to go.
That their arch-rivals East Bengal won at Minerva Punjab FC today, has further compounded Mohun Bagan's misery.
Levelling charges against referee Palmson Raj in their match against Gokulam, Mohun Bagan director Debashis Dutta said that he made "horrendous mistakes", including denying them a penalty in the 35th minute.
"Mr Palmson struggled to keep up with tempo of the game and was often ahead of the play in order to keep up, resulting in wrong decisions and missed fouls," he wrote to All India Football Federation secretary Kushal Das.
"He made another horrendous mistake in the second half when he showed a yellow card to our player Dipanda Dicka, holding him culpable for hand ball. If you look at the TV recording Dicka had clearly chested the ball down," he stated in the mail.
Dutta had earlier complained about "refereeing gaffe" in a mail sent at 6.48pm yesterday for their away match against bottom-placed Chennai City where they dropped points after a goalless draw.
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