Lescott has been linked with a move back to his former club Everton, having lost his starting place at the Etihad Stadium this season.
But, with Yaya Toure and his brother Kolo heading to the African Nations Cup next month, Mancini has no intention of allowing any departures.
"We can't sell players. We don't have enough players to play if we sell players," said the Italian.
And Mancini admits he could bring in a few fresh faces when the transfer window opens, with Jack Rodwell, Aleksandar Kolarov and Micah Richards currently out injured and the Toure brothers, as well as Abdul Razak, on international duty in Africa.
Asked if he might look to bring players in, Mancini said: “Probably - we can have a problem because we lose three players and we have Micah, I don’t think he play until the end of February.
“Jack — we don’t know when he can play. Maybe we can recover [Aleksandar] Kolarov in two weeks. We will see this in next days.”