Gene Simmons wishes he was harder on former Kiss members Ace Frehley and Peter Criss over their substance abuse issues

Kiss star Gene Simmons says one of his biggest regrets is not being harder on Ace Frehley and Peter Criss over the substance abuse problems that led to the talented pair being axed from the band.

Kiss' decades-long career came to an end late last year with a show at New York's Madison Square Garden to wrap up their epic End Of The Road tour.

But guitarist Frehley and drummer Criss were not part of the farewell, as guitarist Tommy Thayer and drummer Eric Singer joined Simmons and Paul Stanley in the four-piece lineup. Thayer replaced Frehley permanently in 2002, while Singer joined the band permanently a few years later.

Reflecting on Kiss' 50-year stretch, Simmons says he has one big regret.

He tells Backstage Pass: "I'm sad in retrospect. You know, hindsight's 20/20. I'm sad that I wasn't more hard on Ace and Peter, the two original guys who played guitar and drums in the band.

"Ace and Peter have as much credit for the beginning of the band as Paul and I do. There's no question it was that chemistry. And they both had unique voices, unique personalities and all that. And they should have been here with us 50 or 55 years later and enjoying the fruits of their labour. But sadly, they're not."

Despite his regrets, Simmons insists Frehley and Criss had themselves to blame.

He says: "They were in and out of the band three different times. They were let go three different times because of the same old thing,.

"It's not even unique. Go to almost every band and you'll find people ingesting stuff more than the bum on the street corner, except they're richer and they can afford to ingest more. It's sad."