Phil Smith is a Special Adviser (and former Policy Adviser) to Peter Mannion, the Secretary of State for Social Affairs and Citizenship. He is a member of the Conservative Party.
Background
Personal
Smith is an avid fan of contemporary pop culture, including fantasy and science fiction (such as Lord of the Rings, The Hobbit, Harry Potter, Game of Thrones, Star Wars and Star Trek) and has a collection of mint condition action figures. His passion for such genres is not viewed upon favourably by his conservative colleagues.
He is also a fan of the music of Wham! and Queen, in addition to dressing up and performing karaoke. Despite working for a conservative political party and in a somewhat serious position, he has a very childish attitude and demeanour.
He shares a flat in central London with his colleague Emma Messinger and another man named Affers. Unsuccessful with women, in Series 4 he remarks that he hasn't had sex in over five years, and doesn't particularly enjoy it anymore.
Professional
Smith was hired by the Conservative Party whilst they were in opposition to work as a Policy Adviser. It is implied he has worked for Peter Mannion in some capacity for many years.