member of the Diet; Diet member; MP
Refers specifically to a member of Japan's national legislature (the Diet). In international contexts, it can also translate 'member of parliament' or 'MP'.
He was elected as a member of the Diet.
Diet members deliberate on bills.
He became a Diet member in his 30s.
The public elects Diet members through elections.
He resigned as a Diet member after the scandal.
I heard she's going to run for a Diet seat in the next election.
国会議員 is the broad Japanese term for a member of parliament, while MP is used specifically for UK or Commonwealth legislators.