"We made a bid in the region of £12m in the summer and the new bid is significantly higher than that," manager Mark Highes has said.
"We have made an improved bid, a substantial bid for Roque Santa Cruz but it was rejected.
"We still want to bring him to the club if we can but he is Blackburn's player and they don't want to deal at the level we have made a bid at. That is their prerogative."