London Irish director of rugby Brian Smith has left the club with immediate effect for family reasons.
Tom Coventry, currently assistant boss of New Zealand side the Chiefs, is understood to be in line to replace the 48-year-old, who was expected to return to Australia at the end of the season.
The Exiles are 11th in the Premiership table with just four wins this term.
"My family has to be my priority right now which is why I asked to be released from my contract early," said Smith.
"I have thoroughly enjoyed my 10-year association with London Irish and will look back on my time with fond memories."
Forwards coach Glenn Delaney will be the interim head coach until the end of the season, with Coventry - who was part of the Chiefs coaching set-up which won the Super Rugby title in 2012 and 2013 - expected to join in time for the start of next season.
Coventry has also been an assistant coach at international level with Samoa as well as taking charge of Hawke's Bay.
|Analysis: BBC Radio 5 live rugby union reporter Chris Jones|
|"Smith has been a central part of English rugby for the past 10 years.|
|"In his first spell at London Irish he established himself as one of the leading coaches in the Premiership and as a result was recruited to join Martin Johnson's England staff in 2008.|
|"Smith paid the price for the poor World Cup in 2011 and on his return to the Exiles he was dealt a tough hand, with Irish struggling to retain their top players.|
|"And even though results haven't been good over the past few seasons, he deserves credit for keeping the club in the top flight."|
Smith, who was England's attack coach between 2008 and 2011, was appointed in March 2012 for his second spell coaching the club.
But the former Australia and Ireland international struggled to recreate the flowing rugby and success of his initial spell, when Irish secured third place in the Premiership and reached the final of the European Challenge Cup and a Heineken Cup semi-final.
The Exiles beat Exeter 28-26 on Sunday with a last-minute drop-goal to end a run of five straight league defeats, with only London Welsh's woeful form keeping them out of a relegation battle and memories of last season's 10th-place finish still fresh in the minds of supporters.
With the Exiles' Premiership status all but assured for next season, the club - with new owners in charge since December 2013 - will now begin the rebuilding process.
"London Irish is grateful to Brian Smith for the contribution he has made to the club," said executive chairman David Fitzgerald.
"He led us to the greatest experience we've had to date of European rugby and introduced some great players to the club.
"We believe that, following Sunday's results at Madejski Stadium and Kingston Park, our Premiership status for next season is more or less secure and allows us to focus on preparing for next season.
"All involved with London Irish, especially the new owners, would like to personally thank Brian for his considerable contribution over the last two-and-a-half years and wish him and his family well for the future."
Smith began his coaching career at Eastern Suburbs in his native Australia before joining the ACT Brumbies in Super 12 in 2001, while his first coaching job in English rugby was as defence coach at Bath.
His spell as England attack coach, as part of Martin Johnson's coaching team, ended unhappily amid the fall-out of the team's troubled exit from the 2011 World Cup, with players criticising his abilities in a leaked report.