The Tories have adopted their own "decapitation strategy" for the election campaign and their top target is education secretary Ruth Kelly.

The Conservatives have now set their sights on ousting senior cabinet members from parliament and the list includes Alistair Darling, the transport secretary; Jack Straw, the foreign secretary; and Charles Clarke, the home secretary.

The strategy marks a decisive change of tactics for the Tories, who have failed in previous elections to home-in on seats with the precision of Labour and the Liberal Democrats.

In a similar strategic campaign in 2001, Labour managed to hang on to almost all of its marginal seats despite a 1.5 per cent national swing to the Tories.