The Robins had said yesterday that they had granted Maynard permission to discuss a move to the DW Stadium.
However, Jackson has insisted that they have yet to make a formal offer for the 25-year-old.
"An informal enquiry was made as to the player's availability last week, but that really is as far as it goes at this stage," said Jackson. "We are therefore disappointed by suggestions that talks are in an advanced stage. Some reports even suggest the player has turned a move to Wigan Athletic, when in fact, no bid has been lodged.
"It is normal for clubs to communicate with each other to ascertain the availability of players - especially during a transfer window.
"However, we believe these conversations should remain confidential, otherwise, as we have seen in this instance, it can lead to exaggerated speculation."
Maynard's contract at Ashton Gate expires in the summer.