When two of the biggest popstars on the planet team up for a charity single, it'd have to be a really bad song for it not to be a hit.

So it came as no surprise to many that Ariana Grande and Justin Bieber's recent release 'Stuck With U' went straight to number one on the US Billboard chart - raising a lot of money for the First Responders' Children's Foundation in the process.

However, one person who was not happy about it is rapper Tekashi 6ix9ine, who has accused the duo of cheating their way to the number one spot - and keeping his own song 'Gooba' from reaching the top of the charts.

The rapper - who has multiple criminal convictions, from sexual exploitation of a child to racketeering, drugs and weapons charges - took to Instagram to make the claims, saying "Understand this: they bought 30,000 or so units on six credit cards. Six credit cards. Now again, you’re gonna enjoy your No.1. Now explain how you buy 30,000 with six credit cards."

However, Grande was not going to take the slander lying down, and addressed them with her own Instagram post.

"I would like to address a few things which I don’t usually do (I don’t give my energy to drama or strange accusations normally but this has gone a little too far)... my fans bought the song," she wrote. "JUSTIN’S fans bought the song. OUR fans bought this song (never more than four copies each, AS THE RULES STATE).

She continued: "[Our fans] are ride or die motherf****** and i thank god every day that i have them in my life, not just when they fight for us to win (even when I ask them not to as I did this week) but because they’re some of the greatest people i know."

It seems that Tekashi 6ix9ine is not convinced, though: