The CST said in the letter: "The current mood amongst supporters is critically low and cannot be ignored. The feeling that the club has become a ‘laughing stock’, both on and off the pitch, is growing.
"The Chelsea Supporters’ Trust regretfully believes that we are close to, if not already experiencing, a significant shift in supporter opinion that could result in irreversible toxicity, almost irrespective of results on the pitch.
"Unless the situation improves, this seems likely to manifest itself in more targeted chanting, especially at televised games, and quite possibly more organised, overt, and impactful forms of protest by some sections of the fanbase."