Ince, who won two league titles and two FA Cups with United in the early nineties, also called his former side a "total mess" because of the ongoing saga between the club hierarchy, Mourinho, Paul Pogba and his agent Mino Raiola.
United lost 3-2 away at Brighton on Sunday in a dismal performance, and reports of disputes over transfers between Mourinho and executive vice-chairman Ed Woodward have been rife throughout the summer.
The relationship between Mourinho and Pogba has been under scrutiny ever since comments made by the Portuguese during the World Cup.
On Tuesday, Raiola increased the tension between his client and the club by hitting out at another former United player, Paul Scholes, who criticised Pogba following Sunday's defeat.
"At Manchester United, everything from top to bottom is in chaos, and it shows," Ince wrote in his Paddy Power column.
“Everyone – from Jose Mourinho not getting his transfer targets to the frustrated players and fans – look unhappy.
"That’s the whole lot, from the top down, Ed Woodward, Jose Mourinho, Paul Pogba, everything is a total mess. You would never have seen this going on with Sir Alex Ferguson as manager, especially not playing out in public.
"Other clubs and fans are having a field day at the minute, seeing what is happening at Manchester United. They’re becoming a laughing stock, and falling behind."