Immigrationboards.com

Hello,

My child was born in the UK. My spouse and I both have pre-settlement status. It seems like we have to apply for our child's pre-settlement status within three months of his birth. However, we don't have any id/passport for him yet, and it will take some time to arrange the European passport. How do we apply for his pre-settlement status within three months without an id/passport?

Thank you.

https://www.gov.uk/settled-status-eu-ci ... d-to-apply

Proof of identity
If you’re from the EU, Switzerland, Norway, Iceland or Liechtenstein, you need a valid passport or valid national identity card.
[...]
If you do not have any of these you may be able to use other evidence in certain situations. Contact the EU Settlement Resolution Centre if you do not have any of the listed documents.

Possibly reach out to them and see if there's anything they can offer; in the meantime you can check with your country's consulate about ways to prove your child's nationality without a passport and if it takes less time (eg nationality confirmation certificate) and maybe that could work.