A phenomenon experienced in Britain from the 1950s to the present day, where the electorate identify less with one main political party and tend to vote much more pragmatically

Back in the good old days when you knew pretty much from birth whether you were going to work down a mine or in a factory etc, people tended to have very strong political allegiances. This would tend to be to the Labour party, if you had a manual labour job or the Conservative party if you had a white-collar job. As a general rule if you were in a trades union you would vote Labour and if you weren’t you would vote Conservative .

As the economic emphasis in Britain shifted, however, from a production economy to a service economy, the number of people in manual labour occupations declined. This meant that the number people who traditionally identified with the Labour party declined. Also the emergence of new ‘white-collar unions’ clouded how being in a trades union affected your voting. This lead to a massive change in direction in the Labour party in the 1980s and 1990s moving further away from their socialist roots to try and appeal to a wider section of British society. This in turn lead to an erosion in the Conservative party's traditional support because of the Labour party's new found closeness to them in the political spectrum.

Information taken from politics classes and Anthony Giddens