David Spade has paid tribute to his late sister-in-law, iconic fashion designer Kate Spade, who was found dead in her New York apartment following an apparent suicide on Tuesday.

The comedian, who is the brother of Kate's husband Andy, took to Instagram to honour Kate, saying she was "so sharp and quick on her feet", while revealing how he can't believe she is gone.

Sharing a picture of the pair at Christmas, David wrote: "Fuzzy picture but I love it. Kate and I during Christmas family photos. We had so much fun that day."

"She was so sharp and quick on her feet. She could make me laugh so hard. I still can't believe it."

 "It's a rough world out there people, try to hang on," David continued.

The 53-year-old Grown Ups actor also took to Twitter to praise his relative, posting: "Katy at my book signing. I love this pic of her. So pretty. I don't think everyone knew how f---ing funny she was... It's a rough world out there people. Try to hang on." 

Kate Spade's niece, The Marvelous Mrs Maisel and House of Cards star Rachel Brosnahan, also paid tribute to her late aunt on Instagram.

Brosnahan posted a video of Kate Spade dancing with the caption: "Knowing Katy, this is how she would want to be remembered. 

"She had a light that words can't capture but touched everyone she came into contact with. 

"She was exceedingly kind, beautifully sensitive, insanely talented, funny as heck and one of the most generous people I have ever known. She was effervescent." 

"Hug your loved ones extra tight today," Brosnahan concluded.

In statement, Kate Spade's family said: "We loved Kate dearly and will miss her terribly," adding that they were "devastated by today's [Tuesday's] tragedy".

The designer and businesswoman had been a well-known name in the fashion world since she launched the eponymous handbag brand with her husband, Andy Spade, in 1993.

A host of fashion designers, political figures and Hollywood stars were among those who paid tribute to the late handbag maker.

Author and activist Chelsea Clinton, the daughter of former US President Bill Clinton, tweeted: "My grandmother gave me my first Kate Spade bag when I was in college. I still have it. 

"Holding Kate's family, friends and loved ones in my heart."

American singer-songwriter Josh Groban wrote that "depression does not discriminate and comes without warning" and sent "love to her family", while posting the phone number for the US National Suicide Prevention Lifeline.

The Good Place actress Jameela Jamil said she was "extremely sad" to hear about Spade's passing, adding she was "an iconic talent".

Actress Lucy Hale from Pretty Little Liars said "mental health does not discriminate and can happen to anyone with any circumstances", adding: "I hope she has found peace."

Girls creator and star Lena Dunham said Spade was "more than a designer" and that she "was also a staple of NYC who spread good will".

Spade is survived by her husband and their daughter, Frances.

If you have been affected by any of the issues raised in this story you can contact Pieta House 24/7 Helpline 1800 247 247 or the Samaritans Helpline 116 123.