50 Cent to Slowbucks -- Hey Liar, I Never Stole Your Damn Chain

Slowbucks is a dirty liar for accusing 50 Cent of masterminding a plot to attack him and stealing his bling ... so says 50 Cent himself.

50 just went on a preemptive tirade against Slowbucks saying the theft allegation is made up and Slowbucks is treading on dangerous territory spreading his story to TMZ and others.

As for Slowbucks ... he claimed he was jumped on June 1 by 50's goons who jacked his gold chain while 50 was onstage at the Summer Jam Festival in Jersey.

Slowbucks tells TMZ ... he's not scared of 50 or his posse, telling us, "People know how I roll in the streets." He says 50 can keep the chain, saying he doesn't want this to escalate into a Tupac/Biggie situation.