The 48-year-old Australian was granted early release on compassionate grounds from his contract that was due to expire at the end of June.
My family has to be my priority right now, which is why I have asked to be released from my contract early.
With seven rounds of the Aviva Premiership remaining, the Exiles are 20 points above relegation favourites London Welsh, who are winless this season, which should be enough of a margin to safeguard their future in English rugby’s top flight.
The Exiles also have the possibility of making a solid run in the European Challenge Cup with ties against Grenoble and Rovigo in the next fortnight.
Glenn Delaney, London Irish forwards coach, will step up as interim head coach for the remainder of the season.
“My family has to be my priority right now, which is why I have asked to be released from my contract early,” Smith said.
“I have thoroughly enjoyed my 10-year association with London Irish and will look back on my time with fond memories.”
In the first spell at the club between 2005 and 2008, Smith took the Exiles to third place in the Premiership and to the final of the European Challenge Cup.
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.
He also led the club to a memorable Heineken Cup campaign in 2007/08, when they were defeated 21-15 by Toulouse at Twickenham.
His success at club level attracted international attention and he was mooted for a role with Ireland before joining the Rugby Football Union as England’s attack coach for three years during the Martin Johnson era.
A return to London Irish followed amid difficult circumstances off the field, and Smith has successfully kept the club in the Premiership
“London Irish is grateful to Brian Smith for the contribution he has made to the club,” David Fitzgerald, London Irish executive chairman, said.
“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.”
The club aims to appoint a new head coach for the 2015/16 season in due course.
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