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Political partisanship is on the decline. The number of voters who would not align themselves with any political party has doubled in the past twenty years, and tripled since Thatcher reigned in Number 10.

That is the finding of this year’s British Social Attitudes survey, which has been tracking the way voters feel about everything from economy and politics to morality for the past three decades.

These numbers contrast with the news that the SNP has won tens of thousands of new members thanks to pursuit of Scottish independence. The party now reportedly has more than 65,000 members – nearly half as many as the Conservative Party.

It is also at odds with this week’s Ukip conference, their most successful to date. We have taken a look at why so many mainstream voters are turning away from the major parties and embracing the Ukippers in both the south-east and the north.