Chelsea face creating "irreversible toxicity" among their fanbase over how the club is run, according to the Chelsea Supporters' Trust (CST).
Runs to Wembley in both the League Cup and FA Cup have masked a difficult first season for manager Mauricio Pochettino, with the Blues 11th in the Premier League.
That is a lowly position for a club that became used to challenging for the title under former owner Roman Abramovich and has spent over £1 billion ($1.3 billion) on new players since a new ownership group took charge less than two years ago.
Chelsea lost the League Cup final to a severely depleted Liverpool last month.
Pochettino has since steered his side into the FA Cup semi-finals but has faced calls to be sacked by the Chelsea support in recent weeks.
And Raheem Sterling was booed off by the home crowd at Stamford Bridge during Sunday's 4-2 FA Cup quarter-final win over Leicester.
Doubts remain over the long-term plan of co-owners Todd Boehly and Behdad Eghbali with fears Chelsea could be hit with a points deduction next season for breaching the Premier League's financial rules.
The CST wrote to the duo earlier this month, warning how a lack of engagement or communication by the club has led to an "overwhelming sense of helplessness, frustration and deep concern" among fans.
This, the CST said, had left Chelsea "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".
The rising cost of ticket prices, coach travel as well as food and drink in general admission areas was also addressed in the wide-ranging letter from the CST, which called for a "supporter communication strategy" that works for both the club and fans.
Chelsea chief executive Chris Jurasek said the west London club deeply valued "the dedication, commitment and desire from all our supporters" and "strives to be the most successful and admired in the world -- both on and off the pitch".
