(UK) If someone, especially a politician, is economical with the truth, they leave out information in order to create a false picture of a situation, without actually lying.
If negotiations between countries or parties are held through press releases and announcements, this is megaphone diplomacy, aiming to force the other party into adopting a desired position.
This phrase is used when one is so cynical that one doesn't think one can change their Representatives. The phrase must have started with frustration towards a local body of government.