Ralf Schumacher feels Christian Horner's position in charge of Red Bull is now "untenable" and he "should resign" in the wake of his investigation.
Horner was cleared of inappropriate behaviour by Red Bull ahead of the season-opening race in Bahrain after the F1 side conducted an independent investigation.
But just 24 hours after there was an alleged leak of messages between Horner and his female accuser that was sent to a host of people in F1 from an anonymous account.
Geri Halliwell showed her support for her husband by turning up to the paddock for Saturday's race and walked hand-in-hand with Horner in a show of unity.
Christian Horner remains under scrutiny at Red Bull
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And Horner gave a defiant response when asked about his immediate future at Red Bull after the race.
However, Schumacher doesn't think Horner can continue as long as the saga continues.
"Christian Horner is now required to really draw conclusions," Schumacher told Sky Germany.
"I think, if you can already see how the mood is against him, that he is not tenable and that he should simply resign now in the interests of the team.
“I think the Thai side [at Red Bull] also has to realise: There’s no point in sticking with Christian Horner."
Red Bull have claimed there are "no issues" and the team is "united", but that didn't appear to be the case with Jos Verstappen over the weekend.
Max Verstappen's father was spotted in a heated conversation with Horner and felt the Red Bull team principals' investigation was "driving the team apart".
Jos Verstappen was also seen in conversation with Toto Wolff after Saturday's race too.
Jos Verstappen was animated in conversation with Christian Horner
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The Mercedes boss then teased a blockbuster move for Verstappen by stating "everything is possible".
Schumacher feels that is a sign that Verstappen is already thinking about leaving Red Bull for Mercedes.
"To me, that means they are already in negotiations," he added.
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Geri Halliwell is sticking by her husband
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"That's plan B if everything else falls apart."
And Michael Schumacher's brother believes Verstappen may not be the only person considering a departure from Red Bull.
"The danger is quite simply that some parties now want to leave and look for new things, new teams, new tasks." he said.
Horner is expected to remain in charge for this week's race in Saudi Arabia with Verstappen facing the media on Wednesday.