Actor Colin Farrell has revealed the full extent of his drink and drug problems and admitted that they threatened to end his life.

The Dublin-born star of Miami Vice was renowned for his wild lifestyle, but made the decision to enter rehab two years ago as he said he knew he was "dying".

"It was a fairly drunken life for 16 years so it was a tough life change, but I was dying and I'm one of the lucky ones in that so far I'm out of it," he said.

"For me there was no choice. I was pretty sick. I went away for five or six weeks and that was a very safe environment and I began to come out of the haze that I had burrowed myself into so deeply.

"I came back into the world and everything was in a degree of focus that I hadn't experienced."

Throughout that period, Farrell became one of the biggest stars in Hollywood, commanding fees of up to $10m to appear in the likes of Alexander and Miami Vice. He dated a number of high-profile women, had a five-month marriage to Amelia Warner and became a father for the first time to James, who is now five.

He now claims, however, that during that time he felt he was always on the verge of a meltdown.

"Desperation will allow you to do incredible things in the name of survival," he told BBC's Friday Night with Jonathan Ross.

"So much of the work that I did I was struggling so hard to keep my shit together. A lot of my energy was going into trying not to have a complete meltdown. By the end of Miami Vice I was just done. "

While his career was hugely successful, Farrell says that internally he was "in pain" and that his nature was the cause of much of his behaviour. "I had created an environment for myself, a way of living for myself which, on the outside, seemed incredibly gregarious and vivacious.

"I don't believe I have any chemical predisposition towards depression, but let's just say I was suffering from a spiritual malady for years and I indulged it.

"To be in pain, if it's self-perpetuated, can be very sweet at times. You can feel very alive when you're in pain, and I also know that from another perspective, like when somebody who I love in my life has passed away.

"There is something incredibly internally vivacious about feeling pain or mourning, even if it's something as egocentric or self-indulgent as mourning for yourself, or pitying yourself."

Farrell is now in a relationship with novelist Emma Forrest and seems to have put those dark tendencies behind him. "I'm glad I'm out of that cycle of my life, and I'm very lucky," he admitted.