The 70-year-old saw his side crash out of the Champions League in December, with questions being raised about the strength and experience of the current Old Trafford squad.
Recent defeats to Blackburn and Newcastle have since handed the ascendency to Manchester City in the title race and Bosnich feels that Ferguson has to take the responsibility for the team's recent form.
“I know a lot of people are too scared to say it, but it starts with the manager,” Bosnich told talkSPORT.
“That singing of ‘Happy Birthday’ before the Blackburn game is too much self-indulgence. I know he’s in his 25th season and so forth but he’s got to start doing what he does best and that’s manage the football team.
“I don’t think he’s got anyone around him anymore, or that any of the players are strong enough to challenge the decisions he’s making and what he’s doing.
"If it goes on like this, they’re already out of the Champions League and they could go out of the FA Cup, they’ll end up winning nothing. Someone close to him needs to tell him.
“He’s [Sir Alex Ferguson] got to pull his finger out if they are going to win anything. He’s very fortunate that Man City lost those points against Sunderland, when they could have won by 10, because that’s what’s keeping them in the title race at the moment.”
United have a chance to get back on track when they face Manchester City in the FA Cup on Sunday at the Etihad Stadium.