Pete Doherty said not being invited to Amy Winehouse's funeral meant he "never had the chance to see through" his grief for the dead singer.
The former Libertines star told the NME that Winehouse, who died last July, "would have wanted me at the funeral".
The singer-songwriter said: "It's a personal feeling of grief I've never had the chance to see through."
Doherty is well-known for his alcohol and drug-fuelled lifestyle, as was Winehouse before her death.
He said: "When Amy died I was sat in a room, a matchbox room in Camden Town, not able to leave, basically wallowing in my own filth. Literally knee-deep in s***.
"I couldn't speak, I couldn't see anyone, I couldn't pick up the guitar and when I did pick up the guitar it was woeful ballads about how Amy wouldn't be coming round tonight, it wasn't a very inspiring time".
The Libertines, whose hits included Don't Look Back Into The Sun, collapsed in 2004 when fellow frontman Carl Barat lost patience with Doherty's wayward behaviour as he battled drug problems.
They reunited in 2010 for a series of gigs but have since gone their separate ways, with Doherty now living in Paris.