Tony Rea, a former head coach and CEO of the club, will be taking over as interim head coach for the last seven games of the Stobart Super League season.
Rob,Powell who joined the club in January 2007 as assistant coach, will remain with London Broncos. Tony Rea, who spent 13 years with the club, is expected to arrive from Australia on Thursday and will be in charge of the squad for the Super League game against Wigan Warriors at The Twickenham Stoop on Saturday.
Chairman David Hughes said: "We had to make changes because our performances were unacceptable. This is a result of our mid season internal review with other findings due to be concluded soon. We are advertising for a new head coach, both in the UK and worldwide, with a view to him being in place for pre-season on November 1st.
"Rob is still part of the team and we hope he will work with Tony for the remainder of the season. He will have a job with the club going forward in some capacity, obviously his specific role will be dependant on the new head coach. Rob is important to the development side of the club along with Phil Jones, and is a valued member of staff.
"I've had regular contact with Tony and he feels for the club. I'm pleased that he has been able to come over and help us out at this time."
Tony Rea, 45, joined the club in December 1994 when they first became the London Broncos. He made 47 appearances at hooker over the next two years before retiring at the end of the first Super League season in 1996 to become chief executive.
At the end of the 2000 season he took over as head coach from John Monie and under him the Broncos made the play offs in 2003 and 2005.
Midway through the 2006 season the club, now Harlequins RL, recruited Brian McDermott as head coach with Tony moving onto the board of directors.
At the end of the 2007 season, he returned to Australia to become assistant coach with rugby union side the Brumbies, based in Canberra. Tony took over as head coach for the remaining games of the 2011 season following the dismissal of Andy Friend.
Since leaving the Brumbies he's been involved in a company called GamePlan-ie who work with businesses focusing on improving performance. On the coaching front he has been working with a number of teams.
Tony admits that getting the call from the Broncos was "a bolt out of the blue" but was eager to help.
"I always check the Broncos' results," he said. "Being down in Australia there are a lot of ex-players. The network's still strong here and we spend a fair bit of time ringing each other and talking about the club.
"I want to get people to enjoy playing again. It's not about tactics, coaching or structure but belief and morale, making sure people re-connect. Knowing the people who support the club I want to validate their decision and help get them to be the club they want to be and Rob will be included in that".