Some info for you @SpanishBureaucracy:
"To put it simply, Spain does not currently recognise Spanish and British dual nationality, and in fact it only recognises dual citizenship from a select few countries that fulfil requirements set out in the Spanish constitution. These include Spanish-American countries, Andorra, the Philippines, Equatorial Guinea and Portugal, and you are also eligible if you are of Sephardic Jewish origin.
So, if you are not on the list above, you have to renounce your original nationality to become a Spanish citizen and, as far as the Spanish authorities are concerned, you would be considered to be Spanish only and would not be considered to be a citizen of any another country."
And:
"But what does this mean for British citizens who wish to apply for Spanish citizenship? And what are the implications and considerations that need to be understood?
Probably the most asked question is… “Do I have to give up my British Passport?”
This is a bit of a grey area, as technically, as part of the Spanish Citizenship application you sign a declaration denouncing your British citizenship, but you do not actually have to surrender your British passport with the application or give it to the Spanish Authorities.
To officially renounce your British Citizenship you would actually complete the relevant documents and pay for this service with the British authorities, not the Spanish Authorities. In fact, it is not an official requirement of the British authorities to surrender your passport to them as part of your Spanish application.
However, you need to be aware that even if you still have possession of your British passport you would not be able to use it in Spain, as this could affect the status of your Spanish Citizenship and you could risk losing it altogether. In the eyes of Spain, if you have Spanish citizenship, you are Spanish and you are not a citizen of the UK so your identity documents or rights as a British passport holder do not apply in Spain.
Therefore, applying to change your nationality or citizenship is not a decision to take lightly, and it is highly recommended that you seek legal advice in both your country of origin and the country of application, as you need to be clear about the rules and regulations and the rights you have in each country in order to make the right decision for you.
For example, if you do officially renounce your British citizenship, although this only affects you and not the other members of your family, it could directly affect the status of future children you may have.
In addition your right to live in the UK would also be affected. You also need to be aware that if you become a Spanish Citizen but then choose to live abroad for 3 years or more you may lose your Spanish citizenship, which would mean you need to go back to your previous nationality or take up another nationality."
Read more here:
www.caserexpatinsurance.com/blog-typical-non-spanish/can-i-have-spanish-and-british-dual-nationality