Vastly experienced former England boss Allardyce - who has a long-established reputation as a relegation firefighter - was appointed to replace the sacked Slaven Bilic in December on an 18-month contract that included a break clause at the end of the season.
The 66-year-old was unable to achieve his aim of keeping West Brom in the Premier League as the club’s immediate return to the second tier was confirmed with three games left to play following a 3-1 defeat at Arsenal earlier this month.
It had been uncertain as to whether Allardyce would be content to remain at the club in the Championship despite West Brom’s desire to keep him in charge and he revealed after Wednesday’s late 3-1 home defeat by Europe-chasing West Ham that he had turned down an offer to stay on for the long-term.
Sunday’s trip to face Leeds at Elland Road will therefore be Allardyce’s final match at the helm, with assistant manager Sammy Lee and first-team coach Robbie Stockdale also set to move on.
“West Bromwich Albion 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,” Allardyce said in an official club statement released shortly after the defeat by West Ham.
“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.”
“I must thank the players and staff, in particular [technical director] Luke Dowling and [chief executive] Ken (Xu Ke), for their unwavering commitment to a very difficult challenge during my time at the club. This challenge was made all the more difficult, of course, by the enforced absence of the club’s fantastic supporters, some of whom I am delighted were present for our final home game against West Ham United.
“The club have asked for my opinion on the qualities my successor will require and I have been more than happy to offer my thoughts. The search for my replacement starts after the final game of the season at Leeds United. In the meantime, we will be concentrating fully on the preparation for that game and will do everything we can to finish the season with as many points as possible.”
Dowling said Allardyce had restored pride at The Hawthorns over the last five months despite failing to prevent relegation and confirmed that West Brom had wanted him to remain in the post.
“Sam, Sammy and Robbie came in at a really difficult time for the football club and worked tirelessly in their efforts to keep the club in the Premier League,” he said.
“Unfortunately, collectively, we were unable to achieve our goal of surviving relegation. In the second half of the season we played with passion and desire, delivering some memorable results with organised, entertaining football.
“Ultimately, we were unable to accumulate the points total required to keep us here, but Sam certainly restored pride with a number of resilient displays.
“Sam, Ken 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.
“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. They will always be welcome at The Hawthorns.”