The couple have parted ways after 10 months of dating because of their "busy schedules", the 31-year-old model has confirmed.
He said: "Sadly me and Molliehavesplit. It just wasn`t the right timing and we were both so busy.
"I have been over in the States three times this month and a relationship can`t take that."
However, David hasn`t ruled out reconciling with The Saturdays singer in the future.
He added to The People newspaper: "Mollie is an incredibly beautiful, lovely girl and so grounded. But it just didn`t work out. Maybe in a few years when we are at different stages in our career we can make it work."
The news comes just two months after David admitted he envisioned growing old with the 24-year-old blonde beauty.
He said recently: "We`ll be spending the next 40 years together.
"I can definitely see us lasting that long. We don`t need to worry about the future."
He also admitted at the time that both he and Mollie put their careers first.
He said: "Both of us work hard and I`m a bit of a workaholic."