Berlusconi wants 'urgent' change at Milan
Allegri has already announced his intentions to leave the Serie A club at season's end, but a press conference has been called for Monday to discuss his future.
Domenico Berardi's four goals inspired Sassuolo to a 4-3 win over Milan on Sunday, seeing Allegri's men slip to 11th on the table halfway through the league season.
And Berlusconi wants immediate change, describing the club's performances as unacceptable.
"A disappointing evening, like others, which confirms that a change is both necessary and urgent with the contribution of everyone concerned," she told ANSA.
"It’s no longer tolerable that our fans participate in performances like these."