The 19-year-old singer had been in a relationship with the dancer-model since they met on 'The X Factor' UK in 2010, but his increasing work load put a strain on their romance, reported Sun online.
"They have been trying for months to make it work but it just hasn't. They had a big chat last month and decided there wasn't any point dragging it out," a source said.
"Liam's on tour until November and Danielle's very busy so they basically never see each other," it added.
This comes after they broke up in September because of the difficulties of a long-distance relationship, although they reconciled in December before mutually agreeing it was over after a two-hour chat last month.
"It was extremely amicable ... Which is good because there's a strong chance Danielle will still be in the lads' upcoming 3D film. The boys are still filming it and editing is going to go right down to the wire.
"But she's been there for most of the filming so it'll be tough to cut her out, and Liam wouldn't want that anyway," the source said.