Teigen, a food writer, TV presenter and wife of singer John Legend, issued an apology this week after she became caught up in a bullying scandal involving a number of fellow celebrities.
Among them was Costello, who alleged that Teigen once made him suicidal after he was falsely accused of using a racist slur.
Singer Lewis, who won The X Factor in 2006, has now claimed Costello’s accusation is “the pot calling the kettle black”.
She accused Costello of leaving her with “deep insecurities” after a perceived snub over a dress she was wearing at a charity fashion show in 2014.
Lewis claimed she was made to feel “very awkward and uncomfortable” as the dress was a sample size and Costello and his team “clearly did not want to alter it”.
At the next fitting, the night before the show, Costello allegedly “refused to turn up” and no longer wanted to dress her, she said.
“He abandoned his commitments to me and the show which made me well aware that I wasn’t the body type required,” she wrote on her Instagram Story
Lewis said she was left “embarrassed” and “deeply hurt” by the incident.
“Because I didn’t look like a model size, I was not permitted to walk in his dress,” she wrote. “I had to sit in the audience and was asked by press why I didn’t walk in the show. I remember having to come up with excuses as I was so humiliated by it all.”
She added: “I was left with deep insecurities after this and I’ve had to work hard over the years to love my body. I know that his (Costello’s) designs are catered to women of all sizes now, and I’m glad he saw the light over the years.”
Costello responded on social media, saying he was “surprised” by the claims. He invited Lewis to contact him privately, offering an apology and adding: “I don’t take accusations of body shaming lightly.”
He shared photos of Lewis wearing one of his designs in 2015, saying he had believed she was “happy” with the look and thought she looked beautiful.
He also shared a number of screengrabs of emails and Lewis’s Instagram posts wearing his designs after 2014. One email from her stylist apparently asking as recently as May this year if he would like to style her for an event.
He also said he is in a “vulnerable moment” and is suffering from poor mental health.
The Independent has contacted Costello’s representatives for comment.
In her post, Lewis said she wishes Costello “so much love and healing”, but also called for Teigen to be forgiven for her alleged bullying.
“We all make mistakes, I know I have, but at this time I feel that when people apologise (Chrissy) and show sincere remorse and rehabilitation for their actions, we should embrace them and not try and kick them when they’re down,” she said.
“Not a day, not a single moment has passed where I haven’t felt the crushing weight of regret for the things I’ve said in the past,” Teigen wrote in a statement earlier this week, addressing the bullying allegations made against her.
She described how “a bunch of my old awful (awful, awful) tweets resurfaced”, adding: “I’m truly ashamed of them. As I look at them and understand the hurt they caused, I have to stop and wonder: How could I have done that?”
Without naming anyone specifically, she noted she has apologised to “one person, but there are others – and more than just a few – who I need to say I’m sorry to”, and said she’s in the process of getting in touch with them.
You can find helpful tips on how to start a conversation, or if you are worried about someone else, on the Samaritans website. You can contact the Samaritans helpline by calling 116 123. The helpline is free and open 24 hours a day every day of the year. You can also contact Samaritans by emailing firstname.lastname@example.org. The average response time is 24 hours.