The Hollywood actor – famous for writing and starring in stoner comedy movies such as Pineapple Express – appeared on Good Morning Britain to talk a out his memoir Yearbook and was asked by presenter Bill Turnbull about his drug use.
Rogen, 39, admitted: "I do, I smoke cannabis all day every day. I have for the last 25 years or so I would say.
Watch: Seth Rogen does ‘not plan’ on ever working with James Franco again
"It's something that is intrinsic to my day to day functionality."
The Knocked Up star went on: "I personally think alcohol - and I know this is the last thing British people want to hear - but on the grand scale of things we put in our bodies to intoxicate or remove ourselves from our normal baseline of functionality, alcohol is not a good one.
"It's high in calories, it gives you a hangover. There are other things we can be putting in our bodies that have less calories and don't make you feel bad the next day, but they are much more stigmatised than alcohol."
And he believes the stereotype that those who smoke cannabis are lazy is rooted in racism.
Rogen said: "The idea that people who smoke weed are lazy or that if you smoke weed all day you're problematic or there's something wrong with you is just not true and it's mostly based on racist lies told by people many years ago that we still unfortunately believe for the most part."
Cannabis has been decriminalised in many US states, including California, where Rogen lives. He is very open about his drug use and has in the past posted imagery of his drug paraphernalia on social media.
TV presenter Turnbull, 65, was diagnosed with incurable advanced prostate cancer in 2017 and has campaigned for the legalisation of cannabis in the UK for medicinal purposes.
The former BBC Breakfast host ingested cannabis via a vape pen as part of a Channel 4 documentary about living with cancer.
Turnbull has said he now takes CBD oil, which is legal in the UK, avoiding THC which is the psychoactive compound in cannabis.
Watch: Seth Rogen on why he doesn't want kids