Actually, the Arabic doesn't say "deny Me", it says "deny" or "be ungrateful." I know that exegesis books are in agreement that "Me" is slighted here, but that's an interpretation.
Whether it is "deny" or "be ungrateful," I think it should be followed by "me" or "to me" since the last letter of the Arabic word would not be there otherwise.
I was just about to post a correction to my argument. You beat me to it!
Indeed, if the meaning were "and do not be ungrateful," the Arabic would have said,
ولاتكفروا. Yes, "Me" must be added and not in brackets because it's actually in the text. The only other possibility, grammar wise, is for the meaning to be "and you are not ungrateful," a present tense sentence. That's not likely.