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Allardyce took over from Slaven Bilic in December, but despite a mini-revival which included a 5-2 win at Chelsea, he was unable to guide West Brom to safety and their relegation was confirmed with a defeat at Arsenal earlier this month.

It is the first time Allardyce has suffered relegation from the Premier League during his managerial career, and the former England boss will not be at the helm next season.

Allardyce's assistant Sammy Lee and first-team coach Robbie Stockdale will also leave The Hawthorns.

West Brom suffered a 3-1 home defeat to West Ham on Thursday (AEST), after which the club confirmed that, despite hoping to keep Allardyce in charge, the 66-year-old will be leaving after Sunday's match at Leeds United.

"Sam, Ken (chief executive, Xu Ke) and I have discussed at length our plans for the future and we very much hoped to have Sam in charge for next season and beyond," said sporting and technical director Luke Dowling.

"Sam and his coaching staff have been excellent to work with and I would like to thank them all for their efforts.

"Sam has given his reasons for leaving and we respect his decision. He has been brilliant to work with and I wish him, Sammy and Robbie all the very best in the future."

Allardyce said: "West Brom made me a generous offer to stay at The Hawthorns that shows the commitment of an ambitious club. After serious consideration I have decided not to accept that offer.

"If I were to stay and achieve promotion next season the expectation would be for me to continue for at least another season and, sadly, that is not a commitment I feel able to make at this stage of my career.

"I believe the club now needs stability and continuity and this would, in my opinion, best be provided by a young and ambitious manager who can get us back to where we should be as an established Premier League football club."