party line 
noun
1A policy, or the policies collectively, officially adopted by a political party: they rarely fail to toe the party line...
- Fundamentally, the Act was designed to enhance the power of the party leaderships and ensure that MPs toed the party line.
- Sectarian organizations with party lines and hierarchical, anti-democratic structures disrupt attempts to move forward collectively.
- Most of them loyally toe the party line for the sake of their careers.
2A telephone line or circuit shared by two or more subscribers.It's like the difference between regular telephone lines and the old party lines that put a bunch of houses all on one line....
- E. used to have the best job a gossip could hope for - telephone operator in a small town in the days of party lines.
- These were all party lines on which everyone up and down the line could, and did, listen in!