Unit 2: Long term unemployment; a supply side problem

From Geoff Riley comes this interesting post on long term unemployment and how difficult it is to cure

http://www.tutor2u.net/blog/index.php/economics/comments/long-term-unemployment/

This BBC clip outlines the government plans

http://news.bbc.co.uk/1/hi/uk_politics/7822692.stm

a) Why is long term unemployment a supply side problem?
b) To what extent can government succeed in reducing long term unemployment using supply side measures?