The former Wrexham boss took the Lambs job in September 2014 and has had them consistently fighting for the play-offs since then.
Tamworth drew 1-1 at home against York City on Saturday but the result wasn’t enough to save Morrell’s job.
They currently sit 12th in the National League North table, seven points adrift of the play-offs and six clear of the bottom three.
The Lambs have only won twice in their last ten League games and a club statement read: “First team manager Andy Morrell has been relieved of his duties with immediate effect.
“The club would like to place on record their thanks to Andy for his contribution and efforts during his tenure and wish him all the best for the future.
“Mike Fowler will assume responsibility for the first team for the foreseeable future, and will lead us into this weekend’s National League North fixture against Alfreton Town.”
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