The resignation was triggered by the government's failure to address what Sunnis consider second-class treatment, and followed weeks of demonstrations, spokesman Aysar Ali said.
The protests began in December when at least seven people were killed in shootings during a protest in Fallujah and have been countered by pro-government demonstrations by mostly Shiite participants.
Sunnis comprise about 20 percent of Iraq's population of more than 27 million, which is about 60 percent Shiite. The protests have raised fears the sectarian division could bring more violence, CNN said Friday.
2014: The Year in Music [PHOTOS]