question tag

I would not use either one. I would write: "He is not sure whether his answer is correct, and neither am I."

Those aren't really question tags [are they?], Ms Tan.

A question tag is a mini question based on the initial statement,

He is not sure whether his answer is correct, is he?

and it could be changed into a regular question.

Is he unsure whether his answer is correct?

He is not sure whether his answer is correct and neither am I.

Or...

He is unsure whether his answer is correct and so am I.

Note punctuation and verbs.

Thanks, Setanta, JTT and Contrex, for your replies.