"I think their have been a lot of mistakes made by a lot of clubs in getting managers who have already been some part of the club in their career.
"I don't buy that. If he's a good manager it doesn't matter who he is, where he comes from or even what nationality he is.
"In fact, in lots of cases, I'd say it was a hardship now to have a club background.
"People say only an old player could do it but maybe it's better to have a clean bill of health.
"Maybe give it to somebody who will really clear the decks."
However Charlton doesn't think that Ferguson will retire in the near future.
He added: "I don't think Alex is even considering retirement at the moment.
"He has a smile on his face and he's enjoying it.
"The last time he said he was retiring I didn't believe it. I was right then.
"But you can't plan for somebody like Sir Alex retiring.
"Some people think it would be the perfect time for him to go if he won another Champions League final. Maybe.
"But he's not a sentimentalist like that. He's hard as nails, Alex.
"He's a born manager. I can't see him thinking of doing anything else for the next few years."