David Oyelowo and Don Cheadle have joined the growing numberof stars who have spoken out against the Oscars for its lack of diversity.
Selma star Oyelowo said: "This institution doesn't reflect its president," referring to African-American Cheryl Boone Isaacs.
"I am an Academy member and it doesn't reflect me. It doesn't reflect this nation."
Cheadle joked about being allowed to park cars at the Oscars on Twitter.
Rock, who is hosting this year's Oscars, took to Twitter last week to joking call the event "the White BET (Black Entertainment Television) Awards".
No black or minority actors have been nominated in the four acting categories for this year's Academy Awards.
Academy president Boone Isaacs has announced she is taking action to "alter the make-up" of their membership, after director Spike Lee and actress Jada Pinkett Smith's refusal to attend because of the mostly white nominees. Criticizes
Boone Isaacs praised the "wonderful work" of the nominees but said she was "heartbroken" at the lack of diversity.
Lee said on Instagram he "cannot support" the "lily white" awards show.
Jada Pinkett Smith said in a video message on Facebook that she would not be attending the awards ceremony.
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"We have a situation whereby currently the biggest movie in the world and of all time (Star Wars: The Force Awakens) is led by a black man. That film was knocked off the top spot this weekend by a film led by two black men, Ride Along 2. The biggest TV show on the planet is led by black people, Empire."
Others who have commented include Will Packer, producer of Straight Outta Compton, who posted a long message on Facebook.
He wrote: "To my Academy colleagues, WE HAVE TO DO BETTER. Period. The reason the rest of the world looks at us like we have no clue is because in 2016 it's a complete embarrassment to say that the heights of cinematic achievement have only been reached by white people. I repeat - it's embarrassing. It's unfair to the performers of colour who sacrificed so much, laid it all on the line AND DELIVERED with their projects this year."
At the weekend, Oscar-winning actor Cuba Gooding Jr told Variety: "You want it (the Oscars) to be diverse. You want the work to show. I wanted Straight Outta Compton to get something. But, you know, it's this conversation that makes people think harder when the nominations come around for next year."
Boone Isaacs added that "dramatic steps" were being taken, saying: "In the coming days and weeks we will conduct a review of our membership recruitment in order to bring about much-needed diversity in our 2016 class and beyond."
The 6,300 members, made up of people from the film industry, vote on who is nominated for the Oscars each year.
"This is a difficult but important conversation, and it's time for big changes," she said.
"As many of you know, we have implemented changes to diversify our membership in the last four years. but the change is not coming as fast as we would like. We need to do more, and better and more quickly."
She said such a move was not "unprecedented" for the Academy, and that in the 60s and 70s younger members were recruited and that today's mandate was about inclusion: "gender, race, ethnicity and sexual orientation".