Culverhouse, picture right, guided the Linnets to the Vanarama National League North title and back-to-back promotions into the fifth-tier in 2020.
However, after a 21st finish last season, the Norfolk side sit in the relegation zone this campaign, currently on a losing run of eight matches.
Chairman Stephen Cleeve said: “There is no doubting that Ian played an important and integral part in our recent history, not least in gaining back to back promotions.
"However, football is a results driven business and given this season’s results and our home form, it was simply not fair to allow the situation to drift any longer for the club or for Ian.
"I would like to place on record my thanks for what Ian has done at the club and would like to wish him well in his future footballing career.”
The Linnets have a short break from league action before facing Dover Athletic on December 11th.