I am applying for a passport and obviously you need to provide your parents details. It asks if my mother has a passport, which she does however it expire around 10-20 years ago. Is this still able to be used for my application or will I need to send my mother's birth certificate instead?
I think the purpose of this section of the form is to verify your parents' information with a view to ascertaining their citizenship and hence your entitlement to a British passport. So it should be fine to put down your mother's expired passport details -- they'll be able to cross-reference that against their records.