The Loose Women star reached out to fans as she shared her grief on social media, and was soon inundated with messages of condolence.
WATCH: Loose Women's Kaye Adams and Denise Welch clash during furious debate on show
Denise posted a touching image showing Kay Mellor hugging her daughter Gaynor and explained: "I've known the Mellors for 24 years since I started Corrie. Absolutely heartbroken for Gaynor and the whole family. A closer knit bunch you couldn't find. RIP Kay."
"Kay Mellor is, was and will always be one of my true writing heroes. So, so gutted. Deepest sympathies to you Denise, and to all Kay's family," one fan remarked, while a second added: "Another sudden death? So sad."
Denise shared a post in memory of Kay Gaynor
A third wrote: "I'm so shocked by Kay's passing. Always admired her work. She was always a writer for the people. A shining talent gone too soon. Sending [love]."
Kay sadly passed away on Sunday at the age of 71. She was known for creating and writing the ITV series Fat Friends - which helped launch James Corden's career.
Kay sadly passed away on Sunday at the age of 71
She started out writing plays, before working on Coronation Street and creating the award-winning children's drama Children's Ward. Her other writing credits include The Syndicate, Girlfriends and Band of Gold. In 2010, she received an OBE.
James was among those to pay tribute, writing on Instagram: "[Kay] was the most generous, kind and loving person. An exceptionally gifted writer. She changed my life when she cast me in Fat Friends on ITV. She saw something in me that no one had before that point.
Fat Friends ran from 2000 - 2005
"She gave so many people their first chances. I have the fondest memories of being on set with her. She will be missed by so many. My thoughts are with her family and friends at this time."
His Gavin and Stacey co-star Ruth Jones, meanwhile, told the PA news agency: "She was a great mentor to me when I first started writing - and always hugely encouraging of new writers - a real testament to the idea of paying it forward.
Ruth Jones described Faye as a 'great mentor'
"Her series Fat Friends was a massive turning point in my career and I will be eternally grateful to her for what she did for me.
"British television has lost one of its greats. Thank you Kay for all that you gave us. I cannot believe you've gone."
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