No, Dave is not right. Tolkien later stated that Morgoth could neither create a new race, nor corrupt an entire people. Offspring of corrupted Elves would be... Elves, not Orks, read the source references I gave you- Sil. is not the scriptures. Tolkien himself was in doubt, I think he ended up deciding that Orks were not intelligent but merely like Dogs or trained monkeys or something like that.
In spite of this, in MY version of M-E, the one that is based on my interpretation and where I game, Orks are bred from debased Elves (though I may change it to Men, another of Ronald's thoughts). However, I know that it is not so- it is merely the easiest solution to a problem that was raised but never clarified.
NT