Basically you need to escape it twice, because it's escaped locally and then on the remote end.
There are a couple of options you can do (in bash):
scp [email protected]:"'web/tmp/Master File 18 10 13.xls'" .
scp [email protected]:"web/tmp/Master\ File\ 18\ 10\ 13.xls" .
scp [email protected]:web/tmp/Master\\\ File\\\ 18\\\ 10\\\ 13.xls .