Sammy Hagar has apologised for exposing his late Van Halen bandmate Eddie Van Halen's "dark side".

The Red Rocker has insisted that while he stands by everything he penned about the late guitar god in his tell-all 2011 memoir, 'Red: My Uncensored Life In Rock, Sammy', he would have only focused on his "genius" and great friendship if he was writing it now.

Hagar told Brazil's 'Inside With Paulo Baron' that "because of the untimely and tragic death of Eddie Van Halen, I apologise from the bottom of my heart for exposing his dark side to where I don't think anyone wants to hear that now, and, unfortunately, it's in the book. And it's true, it's all true. It's not like I have to say, 'Oh, I was lying.' If I wrote the book today, I would only put the good of Eddie Van Halen, because he was such a brilliant, genius guitar player and such a great friend and a great partner, until everything went wrong, like everything else."

In the book, Hagar detailed Halen's drinking habits and the pair's strained relationship.

He said: "No one knew a lot of that about Eddie, but they'd see him on stage and they would think, 'Why is he acting like that?' And I would say, 'Well, you should have seen what happened backstage. Holy f***!'"

Hagar has admitted he would have been easier on the rock icon if he was aware of his ill health.

The 73-year-old singer added: "If we'd have known he was sick then, then I would have understood and I would have been a little more, 'Hey, Ed, come on,' try to reel him in. But he was impossible. He was on a track of just wild. It was tough."

Hagar insisted Halen was "the sweetest guy in the world" when they first met in 1978 but claimed he had another side to him that was like a raging "volcano".

He concluded: "When Eddie Van Halen walked into my dressing room in that show in Anaheim Stadium with Boston and Black Sabbath, that was one of the sweetest people, most humble human beings I've ever met in my life. I thought, 'How can this guy play so badass and be that humble?' I thought, 'It's impossible. He must have a fire inside of him that he's not showing.' And when that fire came out, it was quite the fire — a freakin' volcano."

Halen passed away at the age of 65 in October, following a battle with cancer.

Hagar replaced David Lee Roth as the lead singer of the 'Jump' group in 1985, but left in 1996, before returning for two years in 2003 until 2005.