Backbencher (U.K) – In the U.K, a member of parliament who does not hold office and sits on the back benches of the House of Commons

At the back on a bench (backbencher) the least important members of parliament sit. 

Examples of backbencher (U.K) in a sentence

He became a politician to try make a difference, but he was stuck as a backbencher with little power to change anything.

A backbencher stood up to the Prime Minister over a controversial new law being proposed.

She was quite happy with her position as a backbencher but hoped she would have the opportunity to hold office in the next few years.