Rangers have confirmed that there is a clause in Daniel Cousin's contract that will allow him to leave Ibrox for a set price next summer.
The Gabon international has shone in Scotland since sealing a £1million move from Lens in the summer.
The 30-year-old has bagged seven goals in nine games and that has alerted clubs in England to his ability.
Middlesbrough, Bolton and Derby have all been linked with January bids, amid claims that the clause in Cousin's contract could allow him to leave when the transfer window reopened.
However, although they have confirmed a clause does exist, Rangers have insisted that Cousin cannot leave under the terms of his contract until next summer at the earliest.
"I am disappointed that someone has chosen to bring into the public domain details of a contractual agreement with a player," said chief executive Martin Bain in the Daily Mail.
"There is an exit clause in Daniel's contract but it cannot take effect until the end of the season.
"And the fee required under the terms of the deal is £3million."