Fielder-Civil told talk-show host Jeremy Kyle -- whose program is similar to the Jerry Springer Show in tone -- that he didn't think Winehouse would ever have tried the drug without him.
"I think I might have put up a weak resistance--the fact is, whatever I said, she did end up having some."
Fielder-Civil then detailed how their usage of heroin went up to about once a week, then twice, and progressed from there - and how he felt the initial time he allowed Winehouse to try the drug was a significant point in the singer's downward spiral.
"It started to hurt me and it was more heart-breaking to see," he said. "She had a seizure and was taken to hospital...I put her on her side and called an ambulance. It was due to cocaine -- when it happened I burst into tears, I was completely beside myself."
Fielder-Civil admitted the fact that Winehouse's death was attributed to alcohol made it a bit easier on him; however, he doesn't let himself off the hook. "I don't want to feel like I'm shirking responsibility," he told Kyle.
"Of course I regret it, not just because of the damage it's caused Amy and the loss of life, but the damage to her family, [and] also to my family and also to me."
Fielder-Civil noted he loved Winehouse, but that their partnership had been "complete misery."
Winehouse was found dead in her London home on July 23, 2011. Two inquests into her death -- one dismissed due to the coroner's improper qualifications -- confirmed she died of alcohol poisoning.Related: Amy Winehouse drank herself to death