The Labour government has failed in many ways:
The BNP is a problem symptomatic of a poor government and social system (the last 13 years under Labour) which has failed to control illegal immigration and subsequent negative effects upon the socio-economic sphere which has now the highest levels of unemployed 'young people' and racial violence/intolerance.
The two illegal wars waged by Labour's ex-leader and war criminal, Tony Blair and Labour's flat out ignoring the British public's protests again going to war have led to voter apathy for many years (another reason why people ended up turning to the BNP) because the government fails to listen.
Labour's bed sharing with the financial sector was what allowed, in many respects, the collapse of UK banks, stocks and the massive recession in the British economy.
The Conservatives certainly look more attractive than Labour but David Cameron dislikes directly answering questions.
The Lib Dems are always categorized as "risky" or a "wasted vote" but their voter pool and support base have been steadily growing for years and could provide a surprise if people can pluck up the courage to vote for a party that hasn't fucked up the economy/welfare state/NHS in the last 30 years.