Bookmakers have shortened odds on the likelihood of shadow defence secretary, Iain Duncan Smith, winning an expected post-election Tory leadership fight following a wave of "heavy betting".

William Hill's odds against right-wing leadership favourite Duncan Smith have shortened dramatically from 25 to one on Friday to just two to one by Thursday. The frontrunner remains shadow chancellor, Michael Portillo at six to four.

Tory odds on winning an expected June election are 13 to two the longest odds at any time since 1997. Labour are "odds on" winners at one to 14.

Conservative activists in Bridgewater are planning to take newspaper adverts pledging wavering voters that Hague may still be replaced even if they vote Tory.