Labour MPs are staging a mutiny against Jeremy Corbyn
Benn was fired in a midnight phone call following reports that he was staging a coup against Corbyn.
"I told Jeremy Corbyn last night that I no longer had confidence in his leadership and he dismissed me from the shadow cabinet," Benn told Sky News on Sunday morning.
Shadow health secretary Heidi Alexander was one of the first to step down, tweeting her resignation Sunday morning.
She writes: "As much as I respect you as a man of principle, I do not believe you have the capacity to shape the answers our country is demanding and I believe that if we are to form the next government, a change of leadership is essential."
More than half the shadow cabinet is expected to resign Sunday morning following Benn's dismissal, according to a tweet from BBC political editor Laura Kuenssberg:
Corbyn's decision to remove Benn could cause a revolt in the shadow cabinet. One cabinet member told The Guardian: "A bad-tempered sacking is likely to lead to more trouble for Jeremy."
Huffington Post's Paul Waugh says there are more to follow:
Corbyn is facing a vote on a motion of "no confidence" after Britain voted to leave the European Union. The Labour party campaigned for Remain during the referendum.
"I think the European referendum was a test of leadership and Jeremy failed that test," Labour MP Margaret Hodge told Sky News on Friday.
"There will be no resignation of a democratically elected leader with a strong mandate from the membership," a Labour spokesman told Sky News.