Designer Michael Costello has been "completely blindsided" by Leona Lewis' claims that he bullied her.

On Monday, Costello took to social media to allege that Chrissy Teigen had bullied him so badly in 2014 that he had "thoughts of suicide", and the Bleeding Love singer came forward with her own allegations towards the designer, accusing him of bullying her in the lead-up to a charity fashion show in 2014.

In a post on her Instagram Stories on Tuesday, the British star alleged she was made to feel "very awkward and uncomfortable" at the fitting because "the dress was a sample size and he/his team clearly did not want it to fit me". She then claimed that Costello "abandoned his commitments" because she wasn't the right body type and she suffered "personally and professionally" as a result.

Costello has now responded on Instagram, insisting he was stunned by the singer's allegations, as he believed they had a good relationship.

"I was really surprised to hear about your traumatic experience with me from the Go Red Women charity event in 2014," he wrote. "I fangirled over you and told you how much I loved your songs. You are one of the most talented and beautiful women I know. We took photos and I left options of dresses for you with the charity.

"You told me you absolutely loved the dresses, so much so that even after that event in 2014, you continue to wear and post me on your own IG in 2015... Your team has continuously reached out to me to pull custom looks for you, which I was happy to create. The most recent request I received from you was May 17, 2021."

He included screenshots of the conversations with Lewis' team, and snaps of her on Instagram in his dresses.

"I don't take accusations of body shaming lightly, as I have built a career as celebrating diverse women of all shapes and sizes," he continued. "But if I did unintentionally hurt you and you continued to support me, I want to apologise to you directly. This caught me by surprise, I am completely blindsided."

Costello once again stressed the impact of all the controversy on his mental health, as he added: "I have lost tons of opportunities, sleeples (sic) nights, and I'm not in a good mental state of mind. I wish you spoke to me directly instead of on Instagram, especially when I am at my most vulnerable moment. After years of trauma and getting blacklisted with receipts shown to me by my friends and allies, I have been suicidal and often feel no purpose to live."

Concluding his open letter, Costello wrote: "Whenever you're ready, I'm here. Let's have a heart-to-heart conversation. @leonalewis."

The Project Runway star is also facing further allegations from make-up artist Jordan Liberty, who claimed Costello sexually harassed him while he was going through chemotherapy.

"By the way, Michael Costello called out Chrissy Teigen this week for cyber bullying and has everybody p**sed at her. Meanwhile, he sexually harassed me while I was going through chemotherapy. The gloves are off today," Jordan said in his videos on Instagram, claiming that Costello sent him explicit pictures ahead of a work meeting.

Costello has yet to respond to Liberty's allegations.