here, that there will only ever be two political parties (ie either Labour or Tory) running the country: Given the huge and interwoven economic, social and environmental problems the country and the world has, new political thinking is now more needed than ever. New political movements, like the Green Movement, do come along and new parties do get into government at a range of levels. Liberals have a share in govt now and they currently run Bristol City Council and other councils - and Liberals have been in govt in the past, albeit a long time ago.The labour movement developed over the last 100 yrs, so there is no reason why other movements and parties cant do the same or better.
The Green Party addresses the real world where other parties wish 'for exponential economic growth and endless population growth on a finite planet with dwindling resources' (see online comments here). Greens are making political progress - they have their first MP in Caroline Lucas in addition to Green members of the Scottish Parliament, they are now runnning the council in Brighton and Hove, have two MEPs (Jean Lambert in London and Keith Taylor in the South East), and have two councillors in Bristol (Gus Hoyt in Ashley and Tess Green in Southville) in addition to hundreds more on other councils around the country