The couple, who had been dating for over a year, were rumoured to have broken up over "work commitments".
The McFly bassist announced via Twitter: "I just wanted you all to hear from me, me and Francesca have broken up. It is was too soon for either of us to be seeing people, so please don't believe any of the rumours.
"It was on good terms and she is still one of my best friends x."
Poynter has recently been linked to a romance with Sandford's former S Club Juniors bandmate Stacey McClean.