Phil Brown has been "relieved of his managerial duties" at Hull City.
Hull, who lost to a late Nicklas Bendtner goal at home to Arsenal on Saturday, are 19th in the Premier League, three points away from safety.
A statement on the club website, by Adam Pearson, the club's chairman, read: "Hull City AFC confirms that Phil Brown has been relieved of his managerial duties at the club and has been placed on gardening leave with immediate effect. Brian Horton and Steve Parkin will take charge of first-team duties until further notice."
Brown, in a statement released through the League Managers' Association, said: "I am obviously very disappointed with the club's decision and the fact that I will now not have the opportunity to secure Hull City's status in the Barclays Premier League for a third consecutive season.
"Although I am extremely sad to be leaving Hull City, I am very proud of my achievements during my time as manager, especially having led the team into the top flight of football for the first time in the club's 104-year history and ahead of schedule.
"It has been a fantastic experience and I would like to offer my sincere thanks to all of the players, past and present, and also to my staff. Finally, I would like to thank the fans for their support and wish the club every success in the future."
The official statement on the Hull City website continued: "We would like to place on record our sincere thanks to Phil for the major success achieved during a period of four seasons in charge at the club and wish him every success for the future.
"Promotion to the Premier League in 2008 and retention of our status on the last day of the 2009 season are unique events in the history of Hull City AFC and both were achieved under Phil's stewardship during a period which will never be forgotten by all connected with the club.
"However, retention of Premier League status is paramount and the board believes that a change in managerial direction is the correct option at this time. The club will keep supporters completely up to date in respect of any managerial appointment but, in the meantime, Brian Horton and Steve Parkin will prepare the team for our important game at Portsmouth next Saturday."
