Employer Insurance Refusal Form - violation of privacy?

I have been with my present employer for 18 months. I have always carried my own insurance and signed a refusal form with my employer ( a contracting firm). An immidiate request came in my inbox for me to sign a refusal form - but new twist, it is asking about my husband's insurance ( which I am a part of) policy number, who is covered on the insurance policy etc. Isn't this a violation of MY PRIVACY? Am I legally bound to provide this? Isn't a mere refusal enough??? Can they legally ask me all that? Can I respectfully decline to submit all the details and just respectfully sign the refusal portion? In your answer if you could also state your professional experience ( HR for years, legal for years, conspiracy author etc).