Donald Sutherland wrote to his son Kiefer "every other day" when the 24 star was in jail.
The Dirty Sexy Money actor spoke to Kiefer - who was incarcerated last December for driving under the influence of alcohol (DUI) and violating probation - as often as possible but found it easier putting pen to paper.
He said: "Jail was tough for him. He had 48 days inside, 23 hours a day in solitary. It was very, very cold.
"There were no windows. He had no community. I also made a deposit at the prison so he could call out. We were given 14 minutes for every call.
"When he would call, you weren't prepared and when I got to speak to him I didn't get to say everything I wanted to. I wrote to him every other day though."
Donald, 72, also revealed he turned down the chance to star in 24, which stars Kiefer as counter terrorism agent Jack Bauer, because he wasn't prepared to play a villain.
He explained: "We had a long dinner and he asked me to play his dad in 24.
"I said, 'OK but on one condition, the relationship has to be the same sort of relationship Sean Connery had with Harrison Ford in Indiana Jones.
"He spoke to the writers and came back and said, 'They want you to try and kill me.' I said, 'No way, that's not going to work.' So they hired James Cromwell instead."
Kiefer was arrested last September when he was found to be over the
Californian legal alcohol limit after making an illegal U-turn. He was still on probation for a previous drink driving offence in 2004.
- BANG! SHOWBIZ