***BESTPIX*** Floyd Mayweather Jr. v Conor McGregor 839697146
***BESTPIX*** Floyd Mayweather Jr. v Conor McGregor 839697146

Mayweather-50 Cent feud turns nasty

THE 50 Cent-Floyd Mayweather feud just went up a notch.

The former best friends and one-time business partners have feuded in the past - engaging in Twitter beef that on at least one occasion was fabricated in order to drum up some attention for the pair.

But this time, it seems real. And it's really, really personal - with Mayweather launching a savage attack on the rap star, who himself returned fire with some cutting digs.

The undefeated boxing champion took to social media to brand 50 Cent - whose real name is Curtis Jackson - a 'confidential informant' and a snitch who gossips "like a bitch".

He says 50 Cent is jealous of other rappers and is a fake gangster.

"Curtis "Confidential Informant" Jackson, you're mad because your oldest son Marquees mother doesn't want to be with you!" Mayweather's post begins.

"Your Son, your own flesh and blood don't want nothing to do with you!

"You haven't had a hit song on radio in who knows when and you're definitely not hot enough to even sell records anymore so Interscope dropped you.

Boxer Floyd Mayweather Jr. laughs with rapper Curtis
Boxer Floyd Mayweather Jr. laughs with rapper Curtis "50 Cent" Jackson in happier times. Picture: Getty

"You are jealous of any rapper, athlete or entertainer that's hot or got something going on for themselves. You are a certified snitch and we got paperwork to prove it.

"You talk about Ja-Rule but you stole his whole style and ran with it! You're the only self proclaimed gangster that's never put in work!"

Mayweather, whose net worth is an estimated $US1 billion ($A1.4b), also accuses the rapper of being broke.

"You're always talking about somebody is broke, but the last time I checked it was Curtis Jackson that filed for bankruptcy not Floyd Mayweather," he continues.

"So quick to gossip like a Bitch, why don't you tell everybody how you got Herpes from DJ.

" … I know where all your bones are buried, so be easy Curtis Jackson! And by the way, don't ask to borrow no more money from me."

As expected, 50 Cent hit back quickly - making pointed references to Mayweather's history of domestic violence while posting a picture of the boxer wiping away tears.

Mayweather served a two-month jail sentence in 2010 for a domestic violence assault of former girlfriend Josie Harris - however that is not he has faced court for domestic violence.

"I must have hurt your feelings champ, you had someone write a book I'm gonna take my time with this so I get it all out," 50 replied.

"We are gonna start with your 11 Domestic violence cases. Wait a minute I'll do them in order remember you asked for this. get the strap."