Zahn Malik (22) who left the group's world tour last week due to stress - has announced he is leaving the band to lead a "normal" life out of the spotlight.
He said: "My life with One Direction has been more than I could ever have imagined. But, after five years, I feel like it is now the right time for me to leave the band. I'd like to apologize to the fans if I've let anyone down, but I have to do what feels right in my heart. I am leaving because I want to be a normal 22 year old who is able to relax and have some private time out of the spotlight. I know I have four friends for life in Louis, Liam, Harry and Niall. I know they will continue to be the best band in the world."
The remaining members of the group - Liam Payne, Louis Tomlinson, Niall Horan and Harry Styles - will continue as a four-piece and have reassured fans that their world tour and recording of their fifth album will still go ahead.
They said in a statement: "We're really sad to see Zayn go, but we totally respect his decision and send him all our love for the future. The past five years have been beyond amazing, we've gone through so much together, so we will always be friends. The four of us will now continue. We're looking forward to recording the new album and seeing all the fans on the next stage of the world tour."
However there has been no comment individually from Mullingar native Niall Horan or the other members of the boy band.
Simon Cowell, who signed the group to his Syco label after they came third on 'The X Factor in 2010, admitted he is "truly sorry" to see Zayn leave but is confident the group still have a bright future ahead of them.
He said: "I would like to say thank you to Zayn for everything he has done for One Direction. Since I first met Zayn in 2010, I have grown very, very fond - and immensely proud - of him. I have seen him grow in confidence and I am truly sorry to see him leave. As for One Direction, fans can rest assured that Niall, Liam, Harry and Louis are hugely excited about the future of the band."
Louis Walsh, the 'X Factor' judge, who helped form the group on the reality TV show in 2010, claims he knew the 'Story of My Life' hit makers were having "problems."
The 62-year-old star said: "I knew this was happening. I know everything! Every band has problems."
But Louis believes the British group will continue to be successful as a four-piece.
He told Ireland's Independent.ie: "The Spice Girls had it when Geri Halliwell left. Take Take had it when Robbie left. Westlife had it when Brian left. They all still continued.
"And One Direction will continue now that Zayn Malik has left One Direction. They will go on. The tour will go on."
Meanwhile, Gary Barlow sent his "best" to remaining members Niall Horan, Louis Tomlinson, Harry Styles and Liam Payne following the 22-year-old singer's shocking departure.
The Take That singer, whose group was rocked when Robbie Williams dramatically quit in 1995 and Jason Orange left last year, has no doubt that they will move on.
The 44-year-old singer wrote on Twitter: "Sending my best to all the 1D boys ! #thatters we've all been there haven't we ? !!!!! (sic)"
When a fan then suggested Take That are "proof the show still will go on," he replied: "Well said x"