UFC star Derrick Lewis has been slammed on social media for posting a video showing him spitting in opponent Alexey Oleynik’s food.

American Lewis, who is headlining a UFC Fight Night show against Oleynik in Las Vegas on Saturday night, was mistakenly sent his Russian rival’s meal by the UFC's Performance Institute.

But rather than send the food back, he decided to tamper with Oleynik’s food by filming himself spitting in it, saying he was adding ‘flavour’.

He said: "I believe it's missing some ingredients. We're still going to get him his meal; it's very important. It's fight week, I know he's going to be hungry.

"It looks good, right? I'm going to add some flavour to his food.

"He probably won't even notice. He's from Russia, they don't have any soul food over there."

But the video did not amuse many of Lewis’ followers as he received huge backlash for the clip.

Heavyweights Lewis and Oleynik will square off in the octagon as they look to boost their hopes of a title shot in the division.

Lewis, 35, boasts a professional MMA record of 23 wins and seven defeats stretching back to 2010. 

Meanwhile, Oleynik’s incredible 24-year career has seen him win 59 contests, lose 13 and draw one - a 73-fight stretch which goes all the way back to 1996.