A full list would be very long (but do nominate your favourites by commenting on this blog) but would include
Congress
Mr Smith Goes to Washington (1939)
West Wing (1999-2006)
Charlie Wilson's War (2007)
Thank You For Smoking (2005)
- to say nothing of the various films portraying the lives of members of Congress and Presidents.
Westminster
Cromwell (1970)
Ali G Indahouse (2004) - from Sacha Baron Cohen [Borat; Bruno]
Amazing Grace (2007)
Old Mother Riley MP (1939)
The Chiltern Hundreds (1949)
Whipping It Up (Stage Play)