The X Factor judge and her bandmate are believed to have ended their relationship after repeatedly clashing on a holiday to the Maldives.
© Rex Features / Patrick Rotello/Rex Features
Sources have even told The Sun that the pair "can't stand each other right now".
Contostavlos, who also goes by the moniker 'The Female Boss', appears to have alluded to the break-up on Twitter, writing: "We come we **** **** up.....we leave...#TFBstyle."
The two were first romantically linked in June 2010, but they have both been extremely secretive about their relationship since.
Contostavlos did admit in a December interview that she gets "jealous" and "possessive" over Fazer.
They were believed to be working together on the debut album from Contostavlos's winning X Factor act Little Mix.
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