The Birmingham Mail says Albion have rejected a sub £1million offer from Derby for Thorne.
Thorne signed a three-and-a-half-year deal in January.
He impressed at Derby on loan last season and was arguably the man of the match in the Play-Off Final defeat at Wembley against QPR.
The Rams clearly want to sign Thorne on a permanent basis but Albion say the 21-year-old will be going nowhere.
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