The Baggies lost 1-0 at Cardiff City earlier in the day, their fourth defeat in a row, with the club pinning Clarke's departure on a run of just seven wins from 34 league games in 2013.
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|5/1||West Brom are 5/1 with bet365 to be relegated this season|
A statement published through the League Managers' Association read: "I believe I have unfinished business at West Brom so it is with deep regret that I was relieved of duties as head coach.
"Going into this season expectations were high, perhaps unrealistically so, but with it still being only our fourth consecutive season in the top flight, our primary objective had to be to establishing our status in the Premier League.
"I was, and remain convinced that we were well placed to achieve this aim.
"It has been an honour to manage this club and I would like to thank the staff who have assisted me in every possible way as well as the fans who have been tremendous throughout.
"Now, I wish everyone connected with the club the very best for the future."