The American bad-boy, who found fame on US show The Batchelor, branded the Girls Aloud babe a ‘crack head’ during a now-deleted Instagram live session.
Taking to his official Instagram account, Chad Johnson, 31, raged: “Sarah was f***ing crazy.
“Sarah was f***ing cracked out of her mind – she was a straight-up crack-head.”
After pausing, the controversial reality star added: “I’m sorry Sarah.
“I know that you are already kind of f***ed, but you are f***ing yourself with all the other…[taps nose]… things.
“Chill the f*** out.”
Speaking in an exaggerated British accent, Chad continued: “You can’t be on uppers and downers at the same time Sarah!
“F***ing crazy bitch.”
Revealing he’s cut ties with everyone he met in the Channel 5 house last year, Chad spilled: “I haven’t talked to anyone from Celebrity Big Brother.
“They are dead to me.”
Rounding on Made In Chelsea star Sam Thompson, he vented: “Sam was f***ing weird… a little weasel.”
Sarah’s battle with booze and prescription pills has been well documented.
In 2011 she checked into rehab “for depression and alcohol addiction, as well as reliance on prescription drugs.
Sarah has never spoken about taking illegal drugs.
However, during her time in the Celebrity Big Brother house last year, fellow housemate Jemma Lucy accused her of “only being known for taking a f***load of drugs” and that she “needs to sort her nose out”.
Speaking frankly in 2012 about undergoing treatment in rehab, the troubled star said: “I’m just glad I survived.
“My drinking was out of control and I was addicted to sleeping pills.
“It was an awful combination.”
Comparing herself to the late Amy Winehouse who died in 2011 of alcohol poisoning after years of both substance and alcohol abuse, Sarah added: “I’ve been through something similar.
“I’ve been to hell and back.”
Daily Star Online have tried repeatedly to contact multiple reps for Sarah Harding as well as Sarah directly, however, we have received no reply.