There's no such option, as it's not really optional. It works for me. I'd tell you which Wget version, which operating system and version, and which FTP server I was using, and I'd provide a transcript of the job with a "-d" option, but I figure that you should have to guess all of that, too.
I'm using wget 1.10.2 on redhat enterprise linux 3. But files are all set to chmod 644 although some of them have chmod 755 on the server-side.
Regards Marten