On his Instagram account, Stewart said: “So Greg Wallace is getting fired from Master Chef. Good riddance Wallace…
“You humiliated my wife when she was on the show, but you cut that part out, didn't you? You're a fat, bald, ill-mannered bully.
'Karma got you.
“Mr. Rod Stewart.”
Wallace will step down from the show while complaints from individuals about historic allegations of misconduct at the BBC are investigated.
Wallace, 60, is “committed to cooperating fully throughout the process”, according to a statement from Banijay UK to the PA news agency.
Gregg Wallace quits MasterChef amid misconduct allegations
The statement read: “This week the BBC received complaints from individuals regarding historical allegations of misconduct while working with presenter Gregg Wallace on one of our shows.
“While these complainants have not raised the allegations directly with our show producers or parent company Banijay UK, we believe it is appropriate to conduct an immediate, external review to conduct a full and impartial investigation.
“While this review is ongoing, Gregg Wallace will step back from his role on MasterChef and commit to fully co-operating throughout the process.
“Banijay UK's duty of care to staff is always a priority and our expectations regarding behavior are made clear to both cast and crew on all productions, with multiple ways to raise concerns, including anonymously, and clearly promoted on the set.
“While these are historic allegations, incidents brought to our attention where these expectations are not met are thoroughly investigated and addressed appropriately.”
The statement added: “If anyone would like to talk to us or raise any issues or concerns, they can contact speakup@banijayuk.com in confidence.”