The Scotland international has scored 12 goals from midfield this season, following his £500,000 move from Rangers.
Middlesbrough have tabled a £1.5million bid for the midfielder ... possibly as a replacement for Manchester City target Adam Johnson.
Blackpool boss Ian Holloway: "I've told Charlie about the offer.
"We have a bit of a pact that I want to get him to a club that - if I'm allowed to say it - in a much, much better situation than us. Why leave Rangers to come to Blackpool and then step sideways? Why do that when I think he can step up?
"I think he will still be here at the end of the season. It is normally after 18 months that I lose them."