Gregg Wallace asked a British Sign Language interpreter to sign “big boobs” and “sexy bum” in front of a live audience at the BBC Good Food show, an attender has told the Guardian.

A MasterChef fan who was at the BBC Good Food Show at the NEC Arena in Birmingham in 2012 said Wallace had asked the interpreter if she had to sign everything he said before making the comments. The woman who was in the audience said she had been “appalled and aghast” at “sexist” behaviour by Wallace during the live event in front of about 400 people.

“There was a British Sign Language interpreter there and he wandered over to her at one point and just said: ‘Do you have to sign everything I say?’ And she said: ‘Yes,’ and then he just started saying: ‘Big boobs’, ‘sexy bum’ – this sort of thing, in order to get her to sign it. It was like he could control her, I suppose,” said the woman, a professional in the cultural sector.

“The BSL interpreter is there to interpret what is being said for deaf people,” she said. “They’re not there as a source of entertainment. I just found that deeply disrespectful to [her] and deeply disrespectful to her profession.” .

The woman was so angered by Wallace’s behaviour that she commented about it on social media and tagged the presenter, saying his behaviour had been sexist and rude. In his reply, seen by the Guardian, Wallace asked if she was joking and for details of what happened. After she had replied with the time, date and details of his behaviour, she received no further response. The Guardian contacted representatives of Wallace for comment.

Her mother, who also attended, said she was “outraged” at the MasterChef presenter’s comments. She said she emailed the BBC to complain, but she was not aware that any action had been taken and she had been left disappointed by the response.

A spokesperson said the BBC took complaints seriously and had robust processes to deal with them, but it would be inappropriate to comment on anything that might form part of the ongoing investigation by MasterChef’s production company, Banijay UK.

“We are always clear that any behaviour which falls below the standards expected by the BBC will not be tolerated,” they said. “Where an individual is contracted directly by an external production company we share any complaints or concerns with that company and we will always support them when addressing them.”

The fresh claims about allegations of inappropriate comments come after Melanie Sykes revealed she made an informal complaint about Wallace, saying that having to work with him on Celebrity MasterChef in 2021 was the reason she quit TV. On Tuesday the BBC pulled two MasterChef celebrity Christmas specials, a day after Wallace had apologised for dismissing his accusers as “middle-class women of a certain age”, adding he would now “take some time out”.

Wallace is facing a series of allegations of past misconduct – including three of inappropriate touching – which being investigated by Banijay UK. Previously, Wallace’s lawyers have said he has denied any sexually harassing behaviour.

The woman’s mother said she had complained to the BBC because she felt Wallace had humiliated the BSL interpreter. “How can there be a suitable situation to embarrass a woman like that?” she said. “But to do it on stage in a theatre with 400 people watching – he just didn’t give a damn really about what any women thought or felt, whether they were on stage or in the audience.”

The complainant’s daughter said the public interactions and complaints made about Wallace showed he had been allowed to continue behaving unchecked in a way that caused distress.

“I do think the world has changed quite a lot since 2012 [and] perhaps things that he could get away with then he can’t really get away with now,” she said. “But I didn’t think it was in any way acceptable at the time and I was judging it by my expectations of how people behave in 2012 not by my expectations now.”

The woman added: “I don’t think it’s a witch-hunt. I think it’s a fair and reasonable investigation of behaviour that’s not acceptable.”