A backbencher refers to a politician who holds a less prominent position in government or parliament. They usually sit in the back rows of the legislative chamber, hence the term "backbencher." Full definition
It was Tory backbenchers protecting Tory peers who believe they rule by divine right that scuppered these reforms as before they fought moves to remove hereditary peers. (totalpolitics.com)
Public support for a second vote is likely to embolden Mr Umunna's group of Labour backbenchers who have been urging Jeremy Corbyn to back a Norway - style soft Brexit by pushing for Britain's membership of the European Economic Area. (politicshome.com)
As well as the content of the Statement, it's worth noting the contributions from Conservative backbenchers in the Commons session that followed it. (conservativehome.blogs.com)