Embattled rapper Chief Keef has blamed an addiction to the potentially fatal cough medicine concoction known as "syrup" for the poor quality of his latest music, insisting his most recent releases were "mistakes".

The 18 year old claims his penchant for sipping on the promethazine and soda drink clouded his judgement on his mixtapes Almighty So and Bang Pt. 2 and he now regrets sharing them with fans.

However, he claims he has managed to cut the mixture out of his life for good as he continues to tackle his other substance abuse issues in a court-ordered treatment program.

He tells Billboard.com, "My last two mixtapes were mistakes. I was on promethazine, all drugged out. I was tweaking (high). I don't sip the lean (syrup) no more though (sic)."

Keef was ordered to enrol in a 90-day program in a California rehab centre late last year (13) after testing positive for marijuana while on probation.

However, the rapper has made his feelings about the punishment clear in the title of his new song, F**k Rehab.

He is due back in court on 28 February (14) when a judge will assess his progress.