Leeds finished bottom of the Aviva Premiership on points difference from Newcastle and will be relegated if Worcester win the Championship title.
"I am very passionate about what I do and I have thrived on the challenge over the past three years, however taking all things into account, I feel I have taken Leeds as far as I can," said Back.
"I am very proud of what Leeds Carnegie has achieved over the last three years against the odds.
"The experiences over the last three years have been incredible in terms of my personal and coaching development."
Back, the former Leicester and England flanker, took his first full-time coaching role at Leeds in 2008 and helped the club win promotion in his maiden season at Headingley.
Leeds then defied the odds to retain their top flight status last season but a cruel defeat at Northampton last Saturday - at one stage they had led 24-3 - condemned them to finish bottom.
The club may still earn a reprieve from relegation if Cornish Pirates beat Worcester in the two-legged Championship final on May 11 and 18, because only the Warriors meet the Premiership's entry criteria.
But Leeds are planning for next year on the basis they will be relegated and chief executive Gary Hetherington said Back's departure was best for both parties.
"Neil had a contract with us, he has had three years and for much of that three years it has been a successful time," Hetherington told BBC Radio Leeds.
"The last season has been a disappointing one. There was an option within the contract for either party to come out.
"Neil had given it a lot of thought and taken advice from people he respects and he felt it was the right time for him to come out and probably the right time for the club as well.
"It is an opportunity for him to look at new challenges and new horizons. I have no doubt he will have a long career in coaching.
"It is an opportunity for the club to look again and at our strategy going forward. We are facing up to life in the Championship.
"There was always going to be a restructuring of all our staff and those changes can be made in the knowledge we will have a new coach."
Hetherington said a decision now has to be made as to whether Leeds follow the route they took with Back and give an opportunity to a new coach or opt for a more experienced candidate.
"I think it will be an attractive job and I think there will be a lot of interest in it," said Hetherington.
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