Brentford have rejected a £5.5m offer from Bournemouth for centre-back Chris Mepham, Sky Sports News understands.
The bid included a number of potential add-ons but the Bees have told the Cherries Mepham is not for sale in this window.
Bournemouth have been watching the 20-year-old in recent months, and Eddie Howe scouted him in person earlier in January.
Mepham came through the Championship club's B team - the only one currently in England - and has shone across 13 appearances so far this term.
Bournemouth are yet to sign a player yet in the January transfer window.