Hi there chefkc,
Firstly a warm welcome to the forum.
Secondly, you haven't given much information about the circumstances but may I kindly suggest that as a first step you review the following UKBA pages:-
Can I register a child aged under 18 as a British citizen?
How do I register a child aged under 18 as a British citizen?
I would also suggest you read the UKBA page entitled "Can I be a citizen of two countries?"
There is usually no issue for UK, but you should understand the technicalities of dual citizenship from Philippines view where there are some protocols.
You should review these protocols with your local Phils Embassy
Hope this will help you.