His resignation was submitted by British Foreign Secretary Boris Johnson and he becomes the third minister to resign within 24 hours, turning his back on Theresa May's plans for Brexit.
A Downing Street spokesman said:
"In the afternoon, the prime minister accepted the resignation of Boris Johnson. His replacement will be announced soon. The Prime Minister thanks Boris for his work. "
His resignation is being followed by that of Brexit Minister David Davis and Steve Baker.
His departure came 30 minutes before the British Prime Minister addressed Parliament on her new Brexit plan, which has angered many MPs.