Lambert has activated a release clause in his contract and will step down following the game against Reading on Saturday week
He said: “I would like to place on record my thanks to the owners, and especially the players, staff and fans for the tremendous backing and support I have received since I arrived."
“It’s a brilliant club, with great people, and I wish it every success in the future. For now, I remain fully focused and determined to try to win the final two games of the season, starting this Saturday against Rotherham.”
The former Norwich City and Aston Villa manager signed a two-and-a-half year deal at Ewood Park on November 15, 2015.
Rovers said they will strat the search for a replacement. Meanwhile speculatiion mounts that Lambert is eyeing a return to his old club Aston Villa who were relegated to the Championship earlier this month.