Hollywood star Martin Sheen has told how he felt "powerless" to help his troubled son Charlie during his public meltdown.

Charlie, 49, was the highest paid actor on US TV before he was spectacularly fired from hit show Two And A Half Men over his erratic behaviour.

His father, 74, told Radio Times magazine: "What he was going through at that time, we were powerless to do much. Except to pray for him and lift him up."

The West Wing star added: "You try to be as present as possible. But you have to be aware of the circumstances. You have to be aware of many things that the public is not aware of ... this is a very lonely man. In a very desperate situation.

"Only those of us that knew him understood what was going on."

Sheen added: "I'm talking about steroids, at that time."

He told the magazine: "He was in a very desperate situation. And he was doing what he felt would get him out of it - going public. And it was very painful. No less painful for him."

His son has previously said of his behaviour: "I think I was doing too much testosterone cream, and I think it metabolised into ... a steroid. I think it was a bit of a roid rage. That's the only thing I can point to to explain (it). There was no booze, no pain pills, seriously there was nothing, there was no street drugs."

His father, a recovering alcoholic who has been sober for almost 30 years, told Radio Times: "I wouldn't be human if I didn't have very, very deep feeling for him. And there's something that I understand about that, something the programme (Alcoholics Anonymous) has taught me that's vital in trying to help someone - you can assure them you're there and you love them, but you cannot effect change."

The West Wing star's last TV show, Anger Management, which also featured his son, was axed and he now stars alongside Jane Fonda in Grace And Frankie, a Netflix series about two men who leave their wives for each other.

"Anger Management didn't set the bar that high. I was delighted to work with Charlie - I adore him, and he asked me to do it," Sheen said.

"But we all knew that it was pulled together very quickly to get Charlie (involved), rather than to have a more interesting theme. It was too surface."

He told the creators of his new show that he wanted to see "no fishnet stockings (and) no parading about" in the script.

"I have great love and affection for people in the gay community. So I had a real sense that it was important to get this right. Don't fool around with this. There's no camping here. No flashy stuff," he said.

He admitted that he struggled with some of the scenes in Grace And Frankie, including when a giant pink phallic symbol is installed on his character's lawn.

"I would not participate. Such vulgarity. And I told dear Marta, the writer, it's awful and it's a bad choice. I was honest with her, and I'm glad I was. She looked at me and said, 'Well that's your opinion.' And I said, 'Yes it is, and I'm not participating in that sequence'," he said.

Despite starring in a Netflix show, Sheen said that he had never seen one of its biggest hits, House Of Cards, starring Kevin Spacey as the US president - a role Sheen also enjoyed in The West Wing.

"This is all new to me," he said. "I became aware of Netflix because of a show called House Of Cards, which I understand is about a president. But I couldn't tell you. I've never seen it."