Boateng, who played in the Premier League for Portsmouth and Tottenham, said the Dutchman did not handle his fallout with Ronaldo well.
Ronaldo’s contract was terminated by Manchester United last December following an interview where he made a couple of disparaging comments.
Speaking to Piers Morgan in an explosive interview, the Portugal captain opened up on his tumultuous second spell with the Red Devils.
He slammed the club and Ten Hag for disrespecting him, insisting he felt betrayed by both, before sealing a move to Saudi side Al Nassr on a free transfer.
Manchester United went on to secure Champions League football after finishing third in the Premier League and also won the Carabao Cup under Ten Hag to end a five-year trophy drought.
However, results have not been good enough this season, with the English giants losing six of their 10 matches since the start of the campaign.
Ten Hag’s tough disciplinary lines have also seen him fall out with Jadon Sancho, who remains banished from the first team after challenging the manager on social media.
“He [Ronaldo] was the top scorer and he just kicked him out, he goes against the best player in the team, you don’t do that, you have to give him respect. There are ways to let a player off and I think he chose the wrong way,” Boateng said on Vibe with Five.
“I think he’s got to go. From what I’m seeing, there’s no energy. I don’t see any energy. And then what he did to Ronaldo and all that, it’s too much stuff. I think he’s not on the level to be the coach of Man United.
“Even the team is not the best, they have some good players but not the best. But still there’s no fire. When you come to Old Trafford, it’s like how you said, they put in a ball and there’s no pace, no one gets angry, no one puts in passion and fire. If my players aren’t doing that then me as a coach, I have to do that.”
Boateng announced his retirement from professional football in August following a career that spanned nearly two decades.