Horner was cleared of any wrongdoing following an internal investigation after he was accused of alleged ‘inappropriate behaviour’ towards a female colleague.
The saga has resulted in several key figures’ future being put into disarray, including three-time champion Max Verstappen and chief advisor Helmut Marko, and has caused a supposed rift between the Thai side of the ownership (who reportedly backed Horner) and Red Bull GmbH.
This is what has prompted Newey to express his desire to leave the team, according to BBC Sport, and speaking with Sky Germany, Schumacher blames Horner for Newey’s unrest.
“Adrian Newey needs harmony, he needs a good atmosphere, a workplace,” he said. "And at the moment you have to say clearly: Red Bull is falling apart.
“Christian Horner bears sole responsibility for this because he is clinging to power with all his might.
"I think that won't be the last problem he will have if Adrian Newey leaves him. Max Verstappen is already thinking about it, as is Dr. Helmut Marko, if you watch him like that.
"We remember last year when there were problems. He was sick once and then you immediately saw what was going on with Red Bull. Max Verstappen had difficulties.
"If he [Newey] wants to continue, he has to be free. Otherwise he will of course still be blocked and won't be able to work for a new team.
"I give Red Bull two more years and if they continue to hold on to Horner, then the team will sink into mediocrity. I'm pretty sure of that."