Justin Bieber has accused Taylor Swift of ''crossing a line'' after she publicly branded Scooter Braun a ''bully''.

The 'ME!' hitmaker hit out at the music mogul in a lengthy Tumblr post after it was revealed Scooter had purchased Big Machine Records, who owns the majority of Taylor's master recordings, and now Justin - who is managed by Scooter - has rushed to his friend's defence.

In a note addressed to Taylor, he said: ''So for you to take it to social media and get people to hate on scooter isn't fair. What were you trying to accomplish by posting that blog? seems to me like it was to get sympathy u also knew that in posting that your fans would go and bully scooter. Anyway, One thing i know is both scooter and i love you.

''I feel like the only way to resolve conflict is through communication. So banter back and fourth online i dont believe solves anything. I'm sure Scooter and i would love to talk to you and resolve any conflict, pain or or any feelings that need to be addressed. Neither scooter or i have anything negative to say about you we truly want the best for you. I usually don't rebuttal things like this but when you try and deface someone i loves character thats crossing a line.. (sic)''

The message Taylor posted included an Instagram post of Justin Facetiming Scooter and Kanye West, with the caption ''taylor what up''.

Apologising for his ''hurtful'' message, he said: ''Hey Taylor. First of all i would like to apologize for posting that hurtful instagram post, at the time i thought it was funny but looking back it was distasteful and insensitive.. I have to be honest though it was my caption and post that I screenshoted of scooter and Kanye that said ''taylor swift what up'' he didnt have anything to do with it and it wasnt even a part of the conversation in all actuality he was the person who told me not to joke like that..

''Scooter has had your back since the days you graciously let me open up for you.! As the years have passed we haven't crossed paths and gotten to communicate our differences, hurts or frustrations.''

In her original post, Taylor claims she was never given the choice to buy the masters herself and she is ''sad and grossed out'' that they are now owned by Scooter, admitting it is her ''worst case scenario''.