Vicky Kloss, City's director of communications, was attempting to make contact with boss Roberto Mancini before Sunday's FA Cup tie when she was told by a steward she would not be allowed into the players' tunnel.
City claimed she was told she was being denied entry because she is a woman, which Notts County strongly deny.
County insist Kloss was not prevented from entering the area because of her gender, but because she did not have the right pass.
A County spokesman said: "It's nothing to do with her being a woman. She was trying to get into an area without the correct accreditation."
However, it has been established that Kloss' junior colleague, who is male, had been allowed to enter the same area five minutes earlier without being asked for a pass, which he did not have anyway.