Manchester United fans have called for a vote of no confidence in the club's ownership, and branded Sir Jim Ratcliffe 'an incompetent clown turning the club into a circus'.
Protest group The '58, which has nearly 100,000 members, also announced plans for a demonstration before the game against Fulham at Old Trafford on February 1.
It follows United's decision to sack Ruben Amorim after 14 months in charge, with Ole Gunnar Solskjaer and Michael Carrick competing to replace him on an interim basis until the end of the season.
A spokesman for the '58 said: 'After lurching from one disaster to another, Ratcliffe comes across as an incompetent clown turning the club into a circus. Instead of best in class we're a laughing stock.
'It has been an extraordinary and deeply troubling few days at Manchester United. On the pitch, we are watching mediocre performances from an average team drifting without identity, direction, or ambition. Off it, the chaos is even worse.'
The group also took aim at director of football Jason Wilcox, whose fall-out with Amorim precipitated the head coach's sacking, and chief executive Omar Berrada.
The spokesman added: 'A manager has reportedly been dismissed not primarily for abject performances against Grimsby, Everton, West Ham, and Wolves, but allegedly for a heated exchange with Jason Wilcox, a man with just nine months' experience as a director of football at Southampton who is said to have attempted to interfere tactically, despite the club hiring Ruben fully aware of his rigid system. The situation beggar's belief.
'This decision was allegedly endorsed by Omar Berrada, a CEO with no prior experience in the role, listening to the complaints of a close ally rather than exercising independent leadership.
'We are once again witnessing Manchester United being run by executives learning on the job, at the expense of results, stability, and credibility.
'We call for a vote of no confidence in the ownership, Berrada and Wilcox.
'Let us be clear: this is not a defence of Ruben or the football served up under him. Much of it was unacceptable. But his dismissal once again exposes the continued dysfunction at our club. Manchester United is now a toxic partnership where fans are getting the worst of both worlds.
'The Glazers continue to cream money off the top, while Ratcliffe and Ineos hammer supporters at the bottom. Together, they are running one of the biggest clubs in world football like a local corner shop, penny pinching, short term, and utterly devoid of vision.
'Over $1 billion has already been sucked out of Manchester United at the altar of greed. Jim Ratcliffe has betrayed the hope and faith many supporters placed in him.
'He was supposed to be change. Instead, he has become the perfect Glazer shield absorbing public criticism while Joel and Avram Glazer quietly continue their asset stripping behind the scenes. Nothing has changed. In truth, it is worse.'
Announcing plans for a protest before the Fulham game, the spokesman said: 'We warned about this. We warned where this was heading. Too many are now sleepwalking into the abyss.
'Manchester United is 150 years old. That proud history, built by generations of supporters, must be protected. If we do not act now, the club we pass on will be unrecognisable, stripped of its culture, its soul, and its people.
'For Ratcliffe and the Glazers the game is over. Time is up. We can take no more and urge as many fans as possible to join us in a massive protest.'