UK election: the role of smaller parties

In a UK general election, the first past the post voting system tends to lead to either a Labour or Conservative government.

However, this time opinion polls suggest that the third party, the Liberal Democrats, has narrowed the gap.

This has led to speculation about a hung parliament, where no one party would have an overall majority and the smaller parties could increase their bargaining power.

So, what role are the smaller parties playing in this election?

First broadcast 4 May 2010