LABOUR’S claim in its new poster that “If 1 in 10 Labour voters don’t vote, the Tories win” is claptrap. It relies on highly improbable assumptions, statistical distortions and deliberate confusion.

The Conservatives need to make 158 gains to achieve a Commons majority. The aggregate Labour majority in these seats is 581,000, or about one in 20 Labour voters. On the Labour view, if these voters stay at home or defect to the Lib Dems, the Tories would have a majority. So, Labour argues, its claim of one in ten is deliberately conservative.

Even taking account of local variations and a small rise in the Tory vote, it is virtually impossible to create a plausible situation in which such a switch in votes could put Michael Howard in Downing Street. The figures miss the point: marginal seats do not exist on their own. They reflect general, national, trends. It is nonsense to concentrate on just 158 seats, a quarter of the total, implying that nothing is happening elsewhere. Any shift in votes away from Labour will also affect the other three quarters of seats.

Labour is correct that a fall in its vote could result in some gains by the Tories, even if they do not win any extra votes themselves. The question is, how many? Professor John Curtice, of Strathclyde University, has argued that Labour would lose its overall majority only if one in four of its voters defected or abstained. Labour has been fuzzy about whether it is talking about losing its overall majority or the Tories winning a majority. The two are very different. Even if Labour fell below the 324 seats needed for an overall majority, the Tories might still be at least 80 to 100 behind.

A large swing from Labour to the Lib Dems would also hit the Tories, as support for them would rise sufficiently to gain many seats from the Conservatives. If there was the one in ten switch proclaimed in the Labour poster, Tony Blair would still return to Downing Street with a majority of at least 70, even on his lowest current poll rating.

THE BOTTOM LINE

• In Wimbledon (Labour 3,744 majority) Labour would win by 1,863 if one in ten of its supporters did not vote
• In Gillingham (Lab majority 2,272) if one in ten stayed at home Labour would win by 394
• In St Albans (Lab majority 4,466), if one in ten switched to the Tories Labour would still win
• The Times calculates that just 17 Labour seats out of its 161 majority in 2001 would have been lost to the Tories if one in ten Labour voters had stayed away or voted Lib Dem

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