The singer's former husband, who has been clean from drugs since he stopped taking methadone in January 2012, said: "I've admitted I was there when she had it first time, yeah it was my doing. I don't think she would have ever experienced it without me.
"I had maybe had it three or four times and we were in a hotel in East London and for some reason I think I had about ten pounds of heroin with me which is something we used to do after a club.
"I was smoking it on foil and she said can I try some and I said... I might have put up a weak resistance... the fact is whatever I said she did end up having some.
"I have to be really sort of conscious about what I say. I don't want to feel like I'm shirking responsibility, the fact is what I'm saying is of course I regret it.
"Not just because of the damage it's caused Amy and Ioss of life but the damage to her family but also to my family and also to me. You know we've all sort of gone through this addiction."
On taking drugs with Amy, he said: "I think some people don't know or they don't realise but as far as using heroin or crack goes, I mean the cocaine use was recreational to be honest, out of maybe a six- or seven-year relationship that me and Amy had on and off there was drug use for about four months together.
"We used heroin together as addicts for like four months, then I went to jail, then it got a lot worse while I was in jail and then when I came out of jail, I was told that if I loved her I'd divorce her and set her free and I did.
"Her family and my family said, but specifically her dad said this needs to stop. He said if you love her really you'll divorce her. I spoke to Amy about it and we sort of agreed that it would get everyone off our backs and we'd probably remarry, but I did and we divorced."
After Blake came out of prison and switched his phone on, he had texts from Amy from before her death.
He revealed: "I don't know what dates they were from because when I turned the phone on they were there but there was one talking about being a godmother to Jack (his son).
"We had sort of spoken in the previous weeks about her visiting me and we had had maybe one emotional phone call when we'd said 'are we thinking about maybe getting back together at some point?'"
On going into rehab for the third time and getting clean from drugs for his son and partner Sarah Aspin, he said: "I sort of had to take the thought that my son is going to need me, I don't want my son going to school and for the other mothers at the gates to say 'that's this junky...'
"They probably will anyway because that's the nature of what people are like but I want my son to be able to go to school and say, 'well no matter what they say I know my dad doesn't do drugs'. I want him to be proud of me."