According to Costello, when he tried to explain the incident (which appeared as a racial slur) to Teigen, she dismissed him, allegedly telling him his "career was over and that all doors will be shut from there on".
Costello's lengthy Instagram post claims that over the following years he was "pulled off" jobs last minute with "no explanation".
He also said he would "regularly get texts and calls" from friends and colleagues in the fashion industry who told him that Teigen and her well-known stylist Monica Rose had "gone out of their way to threaten people and brands" against working with him.
"Each time I pleaded with Chrissy Teigen or Monica Rose to see the whole story before believing a false narrative a former disgruntled employee cast upon me, they didn't give me the time of day," he shared.
Costello also shared alleged screenshots of a text conversation with Teigen, where she wrote, "Racist people like you deserve to suffer and die. You might as well be dead. Your career is over, just watch."
The designer shared the impact that Teigen's actions had on him: "So many nights I stayed awake, wanting to kill myself. I didn't see the point of living. There was no way I can ever escape from being the target of the powerful elites in Hollywood, who actually do have powers to close doors with a single text."
In the caption to the post, however, Costello wrote, "You do not have to say anything mean or hurtful about them in the comments I am trying every day to love myself and forget this happened."
Costello's accusations follow Teigen's return to Instagram with a lengthy message to apologise for her past cyber-bullying of Courtney Stodden, among others.
"Hi all. It has been a VERY humbling few weeks," she wrote. "I know I've been quiet, and lord knows you don't want to hear about me, but I want you to know I've been sitting in a hole of deserved global punishment, the ultimate 'sit here and think about what you've done.'"
Stodden, 26, accused Teigen of telling them to kill themselves in private DMs after Teigen had publicly tweeted that Stodden should "take a dirt nap". Teigen publicly apologised to Stodden in May, but Stodden claimed they never heard from her privately.
Where to get help:
• 0800 543 354 (0800 LIFELINE) or free text 4357 (HELP) (available 24/7)
• https://www.lifeline.org.nz/services/suicide-crisis-helpline
• YOUTHLINE: 0800 376 633
• NEED TO TALK? Free call or text 1737 (available 24/7)
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• NATIONAL ANXIETY 24 HR HELPLINE: 0800 269 4389
