For the second consecutive year, no black actors were nominated in any of the four acting categories or for direction.
Clooney said films like "Creed", "Concussion", "Beasts of No Nation" and "Straight Outta Compton" should have got a nomination this year besides actors Will Smith and Idris Elba.
"... I don't think it's a problem of who you're picking as much as it is: How many options are available to minorities in film, particularly in quality films?," he told Variety.
Actor David Oyelowo, whose exclusion at the Oscars for playing Martin Luther King Jr in "Selma" besides director Ava DuVernay had created a controversy last year, too joined in the debate.
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At an event to honour Academy president Cheryl Boone Isaacs, Oyelowo slammed the the lack of inclusion.
"The Academy has a problem. It's a problem that needs to be solved," he said while revealing that Boone Isaacs had met him to discuss his omission from the nominations.
Oyelowo said every actor grows up aspiring to be recognised by the Academy. "I would like to walk away and say it doesn't matter, but it does, because that acknowledgment changes the trajectory of your life, your career, and the culture of the world we live in."
Nyong'o, who won the best supporting actress Oscar for her role in "12 Years a Slave", said she is standing with her peers in protesting the whitewashed nominations this year.
"I stand with my peers who are calling for change in expanding the stories that are told and recognition of people who tell them."
Earlier, actress Jada Pinkett Smith and Spike Lee had called for a boycott of this year's awards show.
"People can only treat us in the way in which we allow."
Lee said it's easier for a black person to become President of the United States than chief of a Hollywood studio or network.
Following the protests, Boone Isaacs had issued a statement calling for speedy changes in the Academy.