Michael Douglas' son credits his father and stepmother Catherine Zeta-Jones for helping him through his ''darkest days'' in prison.

Cameron Douglas - whose mother is the 'Wall Street' actor's first wife Diandra - was jailed for drug possession in 2010 and released in 2016 and is thankful his family never gave up on him, even when he had his sentence almost doubled in 2011 after he was found trying to sell prescription pills to other inmates.

He said: ''My family never gave up on me, not for one second.

''Catherine is a scrapper, she's someone who came from Wales and clawed her way up to the very top through sheer talent and determination.

''She never gives up on anything and she didn't quit on me. The love of my family got me through my darkest days..''

And the 'Chicago' actress also insisted her and Michael's children, Dylan, 17, and 14-year-old Carys visited their 39-year-old half-brother on a regular basis so they could see the reality of his situation.

Cameron told the Mail on Sunday newspaper: ''She didn't want to sugar-coat what I was going through. I made mistakes and there were consequences.

''The kids barely could remember me outside a jail setting..''

Cameron's beloved grandfather, Kirk Douglas, used to visit him at the Metropolitan Correctional Center in New York, but when the 101-year-old actor grew too frail to travel, he still sent his grandson ''at least two letters a month'' to remind him he was ''not forgotten''.

Cameron said of Kirk: ''Grandpa came and he wore shades the whole time, like a proper Hollywood star. He asked me, 'How many fights have you be in - and are you winning?' He's from tough stock.''

But though he was thankful for his family's support, Cameron admits his famous name didn't help him behind bars.

He said: ''If anything it put a target on my back. Celebrity means nothing inside. I found people I wanted to hang out with and they had my back and I had theirs.

''I have kept in touch with some of those guys. When you go through things in jail it bonds you in a way a war bonds men together.''

The 'It Runs In the Family' actor is now clean and sober and has a baby daughter, Lua Izzy, with his girlfriend Viviane Thibes.

And Cameron is determined to get his life well and truly back on track by throwing himself into his career.

He said: ''It's my passion. When I'm acting I feel free and honest. I want to show people what I can do.

''I just want to work. When I got out of jail, no agent or manager would touch me because of my reputation.

''Life stops in prison. People take freedom for granted. I don't. I went through a very dark time but it didn't break me.

''The one thing that got me off the rack every morning was to do one thing that day to prepare for being free. I will never take freedom for granted again.

''Now I want to be the best dad, man and actor I can be. I finally have my priorities in the right order. I want to make my family proud.''