Do you think that a planning department is going to grant planning permission to build a flat in a basement where there will no natural light and very little space???????
Are you living there, ....No?
Then this issue is between the planning department and your neighbour, you’re doing nothing but using it as a tool to get what *you* want, don't make me laugh by pretending you are doing it for altruistic reasons. How likely do you think such a strategy will benefit you rather than annoy people, including the planning department, people don’t react favourably to someone telling them how to do their job.
Accept what is and isn’t your business and what you have grounds to object to, and remember you catch more bees with honey than vinegar, nobody acts favourably to a pushy busybody who won’t accept the answer he is given.