Costello posted what appeared to be direct messages sent by Teigen in 2014, showing the model and TV personality threatening to harm his career.
Teigen, who has been embroiled in a cyberbullying row, has now released a strong denial over Costello’s allegations and said she will take him to court if he continues. She said she will donate any damages to an anti-bullying charity.
Teigen wrote: “No idea what the f*** michael costello is doing. He just released a statement where he didn’t at ALL acknowledge how fake the dm’s were, & now claims to have emails that don’t exist.”
She added: “Please do NOT bully this man under the masquerade of defending me. I’ve taken it ALL. I’ve heard it all. I just beg for you to know the truth.
“Michael, you are now causing actual pain to people who are trying to better themselves. Enough. Or this WILL go further. Not here, but an actual court of law.
“And every dime we win will go to an anti bullying charity focused on turning this shit show into a positive. I wish you peace and healing. I have some places I’ve been attending if you’d like the connects.”
Costello hit back on his Instagram, claiming Teigen is “the same bully she always has been, despite her fake apology to the public”.
In what he said will be his last statement on the controversy before taking a break from social media, he wrote: “I’ll say this again. Chrissy Teigen has gone out of her way to close doors to my career by making calls, sending texts, telling colleagues and companies that if I were attached to a project that she would not work with them. I have receipts of emails and confirmations from these individuals and companies.”
Teigen’s husband, the singer John Legend, defended her on Twitter and said the exchange Costello shared was “completely fake”.
He added: “Chrissy apologised for her public tweets, but after her apology, Mr Costello fabricated a DM exchange between them. This exchange was made up, completely fake, never happened.”
A statement from Teigen’s representatives added: “Chrissy is completely surprised and disappointed by Michael Costello’s recent attack, which includes fictional ‘screenshots’ from 2014 of supposed private messages that Chrissy did not send.
“In October 2014, she did post a comment on Mr Costello’s Instagram when he was publicly accused of making a racist remark. After he denied the accusation, and claimed it was based on a photoshopped comment, Chrissy deleted the comment, as was reported at the time.
“Chrissy has acknowledged her past behaviour and the pain she has caused, but she will not stand for anyone spreading false accusations to further demean her name and reputation.
“Chrissy will continue to do the work she needs to do to be the best person she can be. She hopes Michael Costello can do the same.”
Teigen recently took a break from social media after being accused of bullying people online.
Model Courtney Stodden, who is non-binary, accused her of sending them messages urging them to kill themselves.
Teigen was also criticised for posts about Lindsay Lohan’s self-harming struggles.
In a lengthy apology earlier this week, Teigen promised to personally apologise to anyone she targeted and described the experience as “VERY humbling”.
Following that post, Costello, a 38-year-old US designer who appeared on TV show Project Runway, said Teigen’s bullying of him in 2014 left him suicidal.
He said Teigen accused him of being a racist over a “photoshopped comment” and threatened to harm his career.
British singer Leona Lewis then intervened to defend Teigen and said Costello had humiliated her in 2014.
She posted a lengthy statement to Instagram, claiming he left her with “deep insecurities” after a perceived snub over a dress.
Costello apologised and said: “I don’t take accusations of body shaming lightly.”
Additional reporting by PA