In Westminster parliamentary systems, a backbencher is a Member of Parliament (MP) or a legislator who does not hold governmental office and is not a Front Bench spokesperson in the Opposition. A backbencher may be a new parliamentary member yet to receive high office, a senior figure dropped from government, or someone who for whatever reason is not chosen to sit either in the ministry or the opposition Shadow Ministry.
In most parliamentary systems, backbenchers individually do not have much power to influence government policy. However, they may play a role in providing services to their constituents and in relaying the opinions of their constituents. Some backbenchers also sit on parliamentary committees, where legislation is considered in more detail than is permitted on the floor of the House, and thereby provide valuable input into the legislative process. In addition, since backbenchers generally form the vast majority of the number of MPs, collectively they can sometimes exercise considerable power especially in cases where the policies of the government are unpopular or when a governing party is internally split.
In some legislative assemblies, sitting at the back of the chamber is not necessarily associated with having a minor role. In Switzerland, senior figures sit in the back rows in order to have a better overview and be closer to the doors for discussions outside the plenary. In Germany the faction leaders sit in the front row, but there are no designated places for other senior figures. Originally, the importance of the front rows for the leaders had also to do with the fact that acoustics were often unsatisfactory before microphones were introduced.
The term "backbencher" has also been adopted outside of parliamentary systems. While legislative branches in presidential systems do not share the firm front bench/back bench dichotomy of the Westminster system, the term has been used to denote junior legislators, or legislators who are not part of party leadership within a legislative body.
See also 
|Look up backbencher in Wiktionary, the free dictionary.|