But Leicester are unhappy because Richardson declined to mention that any club buying Hartson will also have to pick up another £3m tab as part of the arrangement Coventry had with Wimbledon when signing Hartson.
Sky Blues chairman Bryan Richardson dismissed the offer as a "joke", insisting he had no intention of selling the Welsh international.
"Considering what they offered, I take it that it was a joke. The bottom line is there is absolutely no way we are interested in selling John Hartson," he said.
But Leicester are unhappy because Richardson declined to mention that any club
buying Hartson will also have to pick up another £3m tab as part of the
arrangement Coventry had with Wimbledon when signing Hartson.
That means in reality Leicester would be paying £4million if they landed Hartson.
Hartson is reportedly keen to leave relegated Coventry, who are paying him on a game-by-game basis.
But Richardson did confirm that Swedish goalkeeper Magnus Hedman was on the verge of moving away from Highfield Road.
He said: "There has been interest from a number of clubs in the London area and we are hopeful something will go through."
Hedman has been linked with Arsenal and Italian sides Fiorentina and Piacenza.