Harlequins director of rugby John Kingston is to leave the club at the end of the season by mutual consent.
Kingston, 47, was promoted from head coach in April 2016 after Conor O’Shea left to become Italy coach.
He led the club to sixth in the Premiership and qualification for the European Champions Cup during his first season in charge.
But a poor run of form this season has seen his side win just seven Premiership matches out of 19.
The club would not comment on when a successor may be appointed.
Currently ninth with just three games to play, the latest of Quins’ 12 league defeats this campaign came against struggling London Irish at home on Saturday, a performance Kingston labelled “not acceptable”.
“The obstacles this season have been well documented and no one has been more disappointed by our results than me,” Kingston said.
“In my opinion, this is the strongest squad ever assembled in all my time at Harlequins and this leaves the club in a sound position to go forward.”
Kingston, who signed a contract extension in January alongside head coach Mark Mapletoft and forwards coach Graham Rowntree, has been a member of the club’s coaching staff since 2001.
In that time, Quins have won the Premiership, European Challenge Cup and Anglo-Welsh Cup.
Harlequins chief executive David Ellis labelled this season as “hugely frustrating and disappointing for everyone”.
“With considerable regret, we have agreed that John should step down as director of rugby,” Ellis said.
“The process to recruit someone new who can take Harlequins to the very top of English and European rugby is in hand.”
Former Harlequins and England winger Ugo Monye
It’s probably been a long time coming now for lots of fans, and perhaps lots of players. Quins’ season has been way below-average.
We are talking about a man who has been at the club for a very long time, and I could wax lyrical about him as a person, but he just has not been able to deliver the goods for Harlequins.
Regardless of how great he has been for the club, if players lose faith as well as board and fans, there needs to be a change. His position had become untenable.