Got residence card. Required to renew passport?

I have a residence card showing that I am the family member of an EEA national, valid until 2016.

If my passport is going to expire before the RC, can my employer require me to show a valid passport as part of their checks on my right to work in the UK, or is it sufficient to show them a valid RC in an expired passport? (Obviously I would need a valid passport to travel, but I'm interested in what my employer is allowed to ask me for.)

Thanks in advance.

Possessing a valid passport and renewing it at right time is always wise. RC in old passport always remain valid until its expiry/fulfillment of the its conditions. Very rarely employers ask about it as long as the RC/visa is valid.