"The only thing I can say is that Monaco have never spoken to me," he told the Evening News.
"They asked for Nicolas on loan about a week to 10 days ago, no loan fee, nothing. They think that's an offer of interest to Manchester City.
"It's just a joke offer and it was treated that way."
Keegan added: "I thought he had a great game last week and if the fans ever needed convincing that he was committed to the cause, they only have to take a look at that game."
The transfer window closes in 10 days time and Keegan is apparently close to a deal for a goalkeeper.