Conor McGregor has lashed out at Dustin Poirier in a dramatic escalation of their row over an unpaid donation.
McGregor had promised to donate $500,000 to Poirier's The Good Fight Foundation to help fund a new gym.
But four months after his vow, McGregor has yet to make good on his promise - and was called out by Poirier.
McGregor initially explained he was waiting a detailed plan as to how the money would be spent, but later ramped up his rheotoric.
He ranted: "You’re ripped you inbred hillbilly. Why do you wink with your ears? You f****** brain dead hillbilly. 500k with no plan in place. Ye hang tight. Fool. You must be new to money. The fight is off btw. I’m going to fight someone else on the 10th. Good luck on your old contract kid.
"My team does their due diligence to make sure every donation meets the mark. My generosity is known. You will pay with your brain for this attempt at smearing my name.
"Shooting ass shelling ass b****. Little b**** kicks from a shell. Good luck when you’re caught. You’re f*****.
McGregor and Poirier are due to clash for a third time on July 10 although the fight has yet to be officially announced.
Poirier signed his contract last month but there has been no confirmation of McGregor doing likewise.
The rivals' row began when McGregor predicted he would stop Poirier in the fourth round of their trilogy fight.
Poirier responded: "That's a fun prediction!
"You also predicted a donation to my foundation and you and your team stopped responding after the fight in January."
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McGregor, who has been preparing for his revenge mission in Dubai, responded: "A donation, not a debt. We’ve been awaiting the plans for the money that never came.
"I do with all my donations... know where it’s going dot for dot, otherwise it goes walking. As is the case with a lot of these foundations, sadly. You took the McG over the belt shows I was right."
Poirier replied: "One hundred per cent never a debt. You offered, we accepted, and like I said your team never responded to our emails regarding the process of where funds would be put to work! July 10th you will taste defeat yet again."
A fan then claimed the fact Poirier and his wife had already thanked McGregor for the donation showed it had been sent.
But Poirier said:" We thanked him because his team reached out fight week to initiate the process but ghosted us the past two months after the fight.
"My foundation has reached out three times since with no reply. We've moved past it! We will be announcing our next goal soon! Its a big one."