Jesy Nelson has quit Little Mix.

The singer took to Instagram on Monday to share the news with fans, explaining she wants to focus on more positive things in her life.

"The past nine years in Little Mix has been the most incredible time of my life," she wrote. "The truth is recently being in the band has really taken a toll on my mental health. I find the constant pressure of being in a girl group and living up to the expectations very hard...

"There comes a time in life when we need to reinvest in taking care of ourselves rather than focusing on making other people happy, and I feel like now is the time to begin that process. So after much consideration and with a heavy heart, I’m announcing I’m leaving Little Mix.

"I need to spend some time with the people I love, doing things that make me happy. ready to embark on a new chapter in my life - I’m not sure what it’s going to look like right now, but I hope you’ll still be there to support me. I want to say thank you to everyone involved in our journey. All the hard work and dedication that went into making us a success.

"To every single fan who came to see us in concert, who listened to our songs and sung their hearts out, sent me messages and supported me along the way I want you to know I love you all so much and I could never have done this without you and I appreciate it endlessly. Most of all I want to say thank you to Jade, Perrie and Leigh-Anne for creating some of the most amazing memories I’ll never forget. I hope that you’ll continue to fulfill all of your dreams and keep on making music that people love (sic)."

The news comes a day after Little Mix performed as a trio on British TV show Strictly Come Dancing and weeks after a representative for the band confirmed Jesy would be taking an "extended break" due to "private medical reasons".

A statement from the band, confirming Nelson's departure, reads: "After an amazing 9 years together Jesy has made the decision to leave Little Mix. This is an incredibly sad time for all of us but we are fully supportive of Jesy.

"We love her very much and agree that it is so important that she does what is right for her mental health and well-being."

The existing bandmates, Perrie Edwards, Jade Thirlwall and Leigh-Anne Pinnock, have also confirmed they plan to continue as a trio, dismissing rumours a full split is just around the corner.

"We are still very much enjoying our Little Mix journey and the 3 of us are not ready for it to be over," they shared.

Little Mix formed on the 2011 series of The X Factor in the U.K.