Gregg Wallace, Penny Lancaster, Rod Stewart. Photo: Mike Marsland/WireImage; Dave Benett/Getty

Rod Stewart is speaking his mind.

The British rocker, 79, took to Instagram on Nov. 28 to share his reaction to news that Gregg Wallace is stepping away from the U.K.’s MasterChef amid allegations of sexual misconduct. In a heated message, Stewart called Wallace out for alleged mistreatment of his wife Penny Lancaster when she was a contestant on Celebrity MasterChef in 2021.

“Good Riddance Wallace … You humiliated my wife when she was on the show, but you had that part cut out didn’t you?” he wrote. “You’re a tubby, bald-headed, ill-mannered bully. Karma got you.”

Reps for Wallace have not responded to a request for comment from PEOPLE on Stewart’s claims.

Earlier on Thursday, multiple outlets reported that MasterChef‘s production company Banijay UK launched an investigation against Wallace, 60, and said in a statement that he is “committed to fully co-operating throughout the process” but would not be involved with the show during that time.

“We take any issues that are raised with us seriously and we have robust processes in place to deal with them,” a spokesperson for BBC, the network that airs MasterChef, told PEOPLE in a statement. “We are always clear that any behaviour which falls below the standards expected by the BBC will not be tolerated.”

Wallace took to Instagram to share a few words with his fans.

“I would like to thank all the people getting in touch, reaching out and showing their support,” Wallace said in a video posted to Instagram. “It’s good of you, thank you very much.”

According to BBC News, they sent a letter outlining the allegations made by 13 individuals who worked with Wallace across a range of shows he presented and hosted over the course of 17 years to Wallace’s representatives on Nov. 26.

In response, BBC News and other outlets reported that Wallace’s lawyers slammed the claims, saying “it is entirely false that he engages in behaviour of a sexually harassing nature.”

“Whilst these complainants have not raised the allegations directly with our show producers or parent company Banijay UK, we feel that it is appropriate to conduct an immediate, external review to fully and impartially investigate,” Banijay UK said in a statement obtained by several outlets, including Deadline and The Hollywood Reporter.

Gregg Wallace.Andrew Matthews – Pool/Getty

One of Wallace’s accusers is Scottish television presenter and journalist Kirsty Wark, who told BBC News as part of its investigation — which they noted was entirely independent of the production company’s current investigation — that Wallace told “sexualized” jokes during filming when she was a Celebrity MasterChef contestant back in 2011.

“There were two occasions in particular where he used sexualized language in front of a number of people, and it wasn’t as if anyone engaged with this,” she said in a video shared in a BBC News article. “It was completely one-way traffic, but I think people were uncomfortable, and [it was] something I didn’t really expect to happen.”

The article further reported that the BBC had previously warned Wallace that two women complained about his behavior in 2018 on the series Impossible Celebrities. The women alleged that Wallace “talked openly about his sex life to staff on the show” and made them feel uncomfortable.

The outlet stated that Wallace apologized at that time and the women who complained were offered counseling.