We should stop giving British citizenship to persons who are not being absorbed into a single British culture (eg through marrying a native English, Welsh, Scots or Northern Irish person), but are turning us multicultural beyond recognition.
We should be giving something similar to the American green card system which is only achievable if you have and retain nationality elsewhere. Therefore if you break the law etc you can be expelled from the country. For most people there should never be the opportunity to graduate to British citizenship ever. Green card style while you retain other nationality all the way. Behave yourself, no problem, Misbehave, we can remove you.
Conditions about having or not having children could and should be attached in order to reverse the current trend of immigrant populations being prolific while natives decline. This would disincentivise those cultures that come here to have large families.
We should also consider retrospective replacement of some (or many) of those with British citizenship with this green card system. Those with dual nationality should be migrated to a green card status as they would not be left stateless.
