Baby born in spain, do I register British or Spanish

I am British/English living in Spain 13 years, my partner is Argentinian lived in Spain over 15 years but still has Argentine Nationality. Our son is due in October, do I register him as British as I would like him to get a British Passport or do I have to register him Spanish or is this not possible due to my partner been Argentinian. I am planning a trip to the UK in December and he will need a passport either British or Spanish. How soon can he have a Spanish passport.

Spanish I guess

Hello Benkris

Your baby has a right to get a British passport and also an Argentinian passport, based on his parents´nationality. Then, once he is one year old, you can apply for his Spanish passport as he was born in Spain, and all those individuals born in Spain have a right to apply for the Spanish Nationality after one year residing in the country in a regular situation.

Regards,