Michael Douglas is still convinced U.S. authorities are "making an example" of his imprisoned son Cameron because of his famous last name.

The 34-year-old actor was ordered to serve five years in prison in 2010 after he pleaded guilty to charges of distributing drugs, but his sentence was doubled in late 2011 after he committed several infractions behind bars, including smuggling medication into his cell.

His lawyers filed an appeal in a bid to overturn the conviction, but the ruling was upheld last month (Apr13) and Cameron Douglas will only walk free in 2018.

Oscar-winner Michael insists his troubled son deserves to be punished for his crimes, but he is adamant the lengthy sentence was overly harsh - and feels sure his famous familial connections are to blame.

In a candid chat with New York Magazine, he explains, "I have gone from being a very disappointed but loving father who felt his son got what was due him to realising that Lady Justice's blindfold is really slipping.

"I'm not defending Cameron as a drug dealer or drug addict, but I believe, because of his last name, he's being made an example (of)."