Ken Clarke's leadership hopes were given a boost today with the publication of a new poll which shows he is the candidate most likely to woo back disaffected Tory voters.

Richard Harrington, the Tory businessman who commissioned the NOP poll, said that voting for Iain Duncan Smith would amount to "voting for a party which is doomed to never being in government again".

In a separate move, the Clarke and Duncan Smith camps confirmed yesterday that the two have agreed to take part in eight head-to-head debates at leadership hustings across the country.